The only tax difference on the Solo 401(k) is on Unrelated Debt Financed Income that occurs when leverage is used, and then only for real estate debit (not other forms of leverage). 

@Bryan Hartlen You will have prorated property taxes, lenders fees, insurance that sometimes has to be prepaid, inspection fees., appraisals etc.Best thing to do is speak with a title company or closing attorney in the area you are looking to get a schedule of fees.

Most even allow flexibility for tenants to pay by ACH or credit/debit card.I'd be happy to address any other questions you might have. 

Then something as simple as Venmo which doesn't charge when sending money with your debit card or if they already have a balance.

@Dave Foster Another question: how does adding a credit for prepaids to the purchase price affect the net gain? 

@Bridget PostonI just usually put in my offer to purchase "seller to pay up to $4000 towards buyers points, pre-paids and closing costs".

I have prepaid some principal but I do not count that as cash in at this time due to the fact it was completely discretionary + since I have a full time job, I was choosing to throw a little bit of spare change towards the mortgage on top of what my tenants were paying me.

. - The Delayed Financing guideline is pretty straightforward (straight from the Fannie guidelines):“The new loan amount can be no more than the actual documented amount of the borrower's initial investment in purchasing the property plus the financing of closing costs, prepaid fees, and points on the new mortgage loan (subject to the maximum LTV, CLTV, and HCLTV ratios for the cash-out transaction based on the current appraised value).”Two key points:• There’s a time and a place for Delayed Financing (DF).  

If you needed to tap into something which was greater than cashflow, you could just cut a check or use the debit card or however your bank would handle it.

The seller can only pay your closing costs and prepaid expenses up to a limit which is different for each loan type and can vary by the down payment.I would recommend you get a cosigner on a single-family home.