Private lender for a short sale?

[Elizabeth Ricci]

New investor question here:

I have found a short sale that, after running the numbers, appears to be a good deal. Since the house "Needs Major Repair," I am not able to get traditional bank financing and thus would need to borrow from a private lender to show proof of funds. I know this property will cash flow very well, and ultimately I would like to hold this property in my portfolio. 

Would it make sense to find a private lender, use hard money, or perhaps find a partner with cash? 

Since it is a short sale, it will take months and months to close, and I do not want to have to tie up someone elseʻs money for so long. (Or would they just start charging me interest right away/ will I be obligated to make payments right away, even though the deal has not closed?)

..What if in 6 months (or more), when the short sale is ready to close, that lender or partner does not want to work with me anymore because they put their money in another investment?

If I show proof of funds from a private lender or partner at the beginning of the deal, does it have to be that same source of money at the end when it is time to pay? 

Thanks so much!