It you think you can re-rent it in three months, then let her pay 4 or 5 months rent to buy out of it, with part of that being a credit for the security deposit money, assuming there are no damage deductions. 

An example of this would be mixing your personal money and LLC money in the same bank account.3.

If you live in the property there are some great owner-occupy loans available, like FHA or low money down conventional loans.

If it is, and I still want the deal, regardless of all these issues, taking some risk if the deal will close, I will put the money to the wholesaler in escrow with a clause that says, if the deal does not close in 2 weeks, the funds will be returned to the buyer, just to be safe..

6 properties over 6 years is impressive.If you continue on this approach, you may be able to do better than 1 property per year if you make more money with your employer and are generating cash-flow from your renttal properties.Why switch strategies if you have something working for you?

I want to pay them a preferred rate of return on their money without giving up equity in the deal. 

I know that I stand to make more money per renovation by just paying for the work, but I'm attracted to the idea of partnering with him for a few reasons.

I'd rather use the money to buy another property(s).....

Although, banks have their place, private money is for a specific purpose and a specific type of investor. 

You're Pushing your potential buyer/buyers to possibly walk away if they can't find solution. more often than not the money you end up missing on, exceeds the 1%-2% coop commission you're trying to save.