I have a trading software that buys and sells loans. There's an auction site where borrowers ask for some money and lenders bid on them until the borrower is fully funded and the auction ends. There's lots of information on each loan request. My trading bot always bids at the highest possible interest rate, if it is outbid, then it just re-bids slightly lower. Once I win the loan parts, I can sell them at a markup. Right now, I sell at the minimum markup, so that with fees I barely make a profit.
What I'm not sure is what markup I should sell? The lower the markup the faster my loan parts sell, but I will get less profit too. On what loans should I bid? Should I bid on a loan auction with a higher interest rate, but which is not going to end for several days, thereby leaving my money stale, or should I bid on an auction with a lower interest rate, but which is going to end very soon. Sometimes in the former case, the borrower might decide to take the loan and not wait until the end of the auction, thereby I could secure a better interest rate than just bidding on the loan auction due to end soon.
I was thinking of framing this problem as reinforcement learning, but I'm not sure how to do it. My goal is to maximiz the profit I make from trading loans. Any ideas?