Looking For a Creative Financing Idea

I have a cousin looking to sell his single family home, He has offer to sell to me with 20k back. I have bad credit and have been working in real estate for about a year which I havent made much money. Is there a way I could use this 20k to fix my credit and buy. I thought about him pulling out the 20k so i can fix my credit. I would even like to use this money to do two closing at once if possible, buy a multi and keep the single. This could be my start up money for investing in real estate but not sure of how to do it.
any advice

Is this an owner financing deal? If a lender is involved, be sure you disclose everything to the lender so its not fraud. The lender will also only lend in according to their appraised value.
Also, if you have bad credit, the only way to do that is pay off what you owe and keep paying on time, over time. If you can get this 20k, I think you can use some to clean up some bills and use the rest to invest.

Lastly, what have you been doing in RE? How much experience do you have in your goals?