IMF Loan

"IMF Loan ability: Gives you $10,000 but you have to pay it back over time."

- In-game description

 (in-game as IMF loan) is the fourth upgrade of Path 2 for the Banana Farm in Bloons TD 6. In addition to a bigger bank capacity of $10,000 ($12,500 with the Monkey Knowledge "Bigger Banks"), the IMF Loan has a special ability where, upon activation, the player is loaned $10,000 ($12,000 with Backroom Deals), at the cost of accruing debt. When in debt, half of the player's earnings to go into paying it off gradually (cost of 40% earnings with Backroom Deals). IMF Loan abilities are still allowed to become activated while the player is in debt, but each subsequent IMF Loan ability usage gives only $5,000 usable credit and additional debt ($7200 with Backroom Deals), as 50% (40%) of each subsequent loan goes toward paying off previous loans, and therefore has no effect.

The special ability has a cooldown time of 90 seconds, and additionally can't be used until the loan is entirely paid off.

It costs $6,375 on Easy, $7,500 on Medium, $8,100 on Hard and $9,000 on Impoppable.

IMF Loan Ability
Upon activation, the player will receive $10,000 but at the cost of $10,000 debt. The ability will recharge after 90 seconds, but can only be activated again if all of that IMF Loan Bank's debt is paid off. Both the loan and the debt will increase to $12,000 with the Monkey Knowledge "Backroom Deals".

How the "debt" works is that 50% of all income gained (40% of all income gain with Backroom Deals) from all sources will be used to pay off the debt. The amount of income used to pay off the debt is paid off onto the first IMF Loan that owes money and then onto any other subsequent in-debt IMF Loans after paying off the first IMF Loan. The in-debt penalty will remain until all of the debt is paid off from all IMF Banks. The amount of debt is displayed to the right of the cash counter on the top of the screen. The amount of debt of a certain IMF Loan Bank is shown in the respective IMF Loan Bank. Note that you can still sell an IMF Loan Bank while any of the loans are in debt (including itself), but the loan debt will remain until fully paid off. Fortunately, it is impossible to lose as a result of not paying off IMF Loan debts because bankruptcy is non-existent in BTD6.

Unlike normal loans, the player cannot manually pay off the debt of a certain IMF Loan Bank. However the total debt can be paid off quickly by repeatedly depositing and withdrawing from any bank using Bank Deposits.

The ability cannot be used if the player still has debt from the IMF Loan Bank.

Strategy
IMF Loan is a tricky ability to master, as though it is an ability explicitly about gaining money in a large burst, it effectively cancels out the profit with the penalty of a loan which halves the gains of all revenue sources (including other IMF Loan abilities) by paying itself off, leading to an ability that has a net total of zero change in the long-run.

However, the use of the ability can be one of the most powerful in some regards, as it provides the player with a powerful utility: sudden income for panic purchases or reinvestment into other Banana Farms. For the former, having an extra $10,000 to use in the now can be a major game changer, providing a large portion of cash for the cost of expensive, powerful towers, potentially allowing a defense to hold out where waiting for $10,000 to come naturally would be irrelevant since the player would have lost the game.

On the other hand, it provides a high risk in crippling economic gains in favor of long-term revenue but can help to pay off the debt the ability itself creates. This can also be seen with the use of the ability to upgrade the IMF Loan building itself into a Monkey-Nomics building, providing anywhere from an eighth to one-twelfth of the total cost depending on difficulty cost modifier, as well as opening the Tier 5 ability to help pay off the resulting debt quickly.

One important factor that can help increase the effectiveness of the IMF Loan ability is a piece of Monkey Knowledge, being Backroom Deals. With Backroom Deals, $12,000 is loaned off at a time, effectively increasing the potency of the ability by 20%. This also is compounded with a 40% payoff rate and the resulting $12,000 debt, making payoff much longer but also far less taxing if more money is required during the payoff period. With this in play, it exacerbates both positives and negatives of the ability, though the benefit far outweighs the damage, as an extra $2,000 can allow for earlier high-cost purchases on revenue building towers and set up for a heavily prepared late game.

Efficiency
The following are tables regarding the income production rate of the normal Monkey Bank function of the IMF Loan upgrade. In general, it has a higher bank capacity but a similar income production rate to Monkey Bank. As such, its bank functionality does not become more efficient than Monkey Bank until its own bank balance surpasses the Monkey Bank's maximum bank capacity.

Income earning per round (12.0 and later)
As of Version 12.0, bank income bonus has decreased from +$160 to +$150 by default, including for IMF Loan. Therefore, instead of at least $240 per round, this income gain is decreased to at least $230 per round.

Note: The table assumes that the IMF Loan has been initially upgraded before the round starts and that the income is given as when after the round.

Also assume that no manual deposits from the Bank Deposits MK are done. 

As of Version 17.0, the buff to Monkey City allowed nearby income-producers, such as IMF Loans, to gain +10% more income per round. This applies for the income bonus, and it stacks on top of the current interest rate (in addition to interest buffs from Benjamin, if applicable).



Bank Deposits MK (19.0 onwards)
Adding Bank Deposits will almost always increase profit per round. However, after some testing and calculating, the most efficient strategy has made itself apparent, To save space in the table, assume that all farms have the 2/4/0 upgrade.

The money is shown as the amount in the bank at the end of the round (after interest has been applied) and as if all deposits happened during the first round.

Calculations about the average profit per round for each scenerio have been made. It is concluded it is more efficient to withdraw 1 round before the bank reaches its maximum capacity. The profit per round can be calculated by subtracting the amount of money in the bank by the amount deposited, then dividing by the round you withdrew on.

Example math: 2/3/0 bank after depositing 4750. withdrawing at the end of round 4. 9004-4750 = 4254, 4254 / 4 rounds = 1,063.5, rounded to 1,064 per round

Income earning per round (11.0-11.2)


Income earning per round (pre-11.0)


Sounds
When activating IMF Loan Ability:
 * [Cash collecting]

Trivia

 * IMF stands for International Monetary Fund, and it loans money to countries with troubled economies.
 * However, since the game is based off of monkeys, it could stand for International Monkey Fund in the game.
 * The IMF Loan's loan does not work like a real-life loan for the following reasons:
 * Real-life loans require all of the loan plus interest to be paid off until the loan debt reaches the maximum loan debt allowance, which otherwise would lead to financial consequences such as bankruptcy.
 * Interest as increased debt for real-world loan debts tends to increase over time; IMF Loan debt remains constant between the end of a round and the beginning of a round.
 * Paying off the IMF Loan debt decreases with the increase of income gain (from any source or income gain), rather than not gaining income as debt is being paid off.
 * Such automatic paying off the loan is always 50% of the income earned, but automatic paying off loans does not exist or is not commonplace.
 * One can basically not pay back an IMF Loan for however amount of rounds as the player wishes without losing from forced bankruptcy.
 * Assuming the IMF Loans are run by the same company, it is impossible to pay off a loan with an existing loan.
 * In Version 7.0, the Monkey Bank received a nerf to the amount of bank capacity, leading to the Monkey Bank to have an overall lower bank capacity. This was not the case for IMF Loan, causing an indirect buff to the IMF Loan.
 * The normal Monkey Bank now has $7,000 in capacity while the IMF Loan still has $10,000.
 * Using multiple loans at once will grant the full $10,000 from the first ability, but each subsequent loans will be affected by the other loans, granting $5,000 ($6,000 with Backroom Deals) and will only increase the total loan by $5,000 ($4,000 with Backroom Deals) rather than $10,000.
 * This is because 50% (40%) of the loan is being used to pay off the existing debts.
 * There was a known bug related to IMF Loan in Co-Op where towers can disappear when the server refreshes the map to sync the game if there is an IMF Loan present on the map. This seems to be patched around version 12.0.
 * "Loan" in IMF Loan is not capitalized and this is the only upgrade that has this error.
 * It is possible to easily reach the maximum usage limits per round for the IMF Loan ability by doing the following: activating an IMF Loan ability, pay the debt off manually with Bank Deposits, and wait for the abilities via stalling the rounds. Then after two usages, the ability will become disabled for the rest of the round.
 * Only one loan can be paid off at a time, any additional money gained in one large sum (e.g. selling towers, collecting all bank funds at once) will directly go to the player without paying off additional loans at a 50%/40% rate.