simple math formula calculation - Find advance amount - ROI

Generate simple math Formula Problem:calculate the largest Advance Amount possible provided by an investor for a business based on known investor expected Return and based on the amount of money a business has in a pending invoice( money owed) Investor goal is to get the largest possible advance of course against his pending invoice (not include time element ...bonus if you can) What known: 1. Investor Expected Rate : 1.5 or 1.6 or 1.8, 2.0 which means an investor make x his advance rate on loan money example Investor A provide advance $100 and his expected Return Rate his 1.8 he would make $180 back on his investment or $80 profit on the advance amount of $100 2. What else we know is Total money in an invoice owed to the business The business does not want to wait and he wants the largest advance against his money now! Just a # ..example $260 or $500 or whatever.. What not known? is what is the largest advance the investor can provide based on his expected rate of Return(x 1.5, x 1.6, 2.0 x, etc) Provide us the math formula so if we know the total money in an invoice an advance, the expected rate of return of the investor what would be the formula to calculate the largest advance the investor can provide the business owner based on his expected return rate? Extra Bonus: not included: if you know how to include time element till investor collect on his advance into calculation - extra $$$ Time can be varied...3 months, 6, 9 months , etc.. $10-$30 quick answer with top grade