You could either do a Joint Venture (JV) structure as an active partner. 

From a tax perspective, splitting the properties exactly in a 50/50% partnership might not be possible (unless you want joint owners ship and that will create another partnership).

If he were to wrap the existing loan in an installment sale to you, then use a loan servicer to collect your payments that could be set up on automatic ACH, plus pay the underlying before dispersing funds to him each month, before long he'll forget the underlying exists.

Some younger investors use a joint venture partner to help supply the down payment.

However, you must meet both tests during the 5-year period ending on the date of the sale.”https://www.irs.gov/taxtopics/tc701If you are married and file jointly, “Section 121 sale” would get you exactly $500k tax-free, but you’ll need to recapture any depreciation, which, I imagine, would not be much.

This can be a joint venture contract or you can structure it as an LLC to purchase the property, and you both own the LLC.

ACH is freeTakes about 5-7 days for the funds to hit your bank accountExcelI use an excel spreadsheet to track my check register.

Most rental agreements are jointly and severally liability of all adults.

(Tenants in Common or Joint Tenants ... this has implications should one of you die.)Good luck!

I would suggest using a Margin Loan first if you have an Individual or Joint Taxable account.