Completely eliminated noise complaints from the lower level and reduced utility costs.

Make sure your rehab is "renter" cost rehab. etc. 

Way better returns on the cost seg than you'd ever cash flow from an LTR. 

to save costs, and responses sometimes took weeks.

Determine cost to renovate. 

For a 30 year Conventional loan, I'm at 6.5% rate (6.808% APR) for a duplex, 95% LTV, 780+ FICO, owner occupant.And I'm assuming they're paying $2k of your closing costs - not your down payment.

However what happens when the tenant vacates and now the unit has to be turned over/takes a few months to find a new tenant and during that same period of time the sewer line goes and you get hit with that $15,000 cap ex expense in addition to the vacancy and turn over costs.

Whether the seller was open to a buyer commission or not, I wouldn't put an additional cost into any personal purchase.  

While this can maximize leverage and ROI, challenges include getting lender approval for seller financing, high carrying costs, and the pressure of short-term loans.

You will also need about 6 months of reserves deposited in a traditional financial institution rather than a crypto account.The next step is to find the target property and calculate the acquisition costs and costs of construction along with the after-repair value.