a single family to a multifamily property is perfectly fine.Lastly to your question - You must purchase at least as much replacement investment real esate as you sold if you want to defer all tax.  

@Josh Roman I have one that’s two houses with three units on one tax parcel linked to a second tax parcel that has always been on one mortgage.

Same school district, property taxes etc.

I don't want to go into debt to pay for college.

If you don’t have any debt on your properties and you feel comfortable taking the risk of self insuring, you are still ignoring the greater risk from liability claims.

I think most of his flips are in inexpensive cities like Cleveland, Detroit area, etc. https://flipsystem.com/faq/I think $10,000 to $20,000 (before IRS taxes) is a really small profit margin.

About $900 a month after taxes/insurance/and misc repairs. 

@Pyrrha RiversHi Tokyo / Japan BP members..Just an update - we started a closed FB group to help out of country investors connect, ask questions, etc.If you'd like to join, here's a link:https://www.facebook.com/groups/seoulreigroup/We just posted two spreadsheets to help with quick financial analysis / estimating owner debt load.

You should make sure that the rental revenue meets all of your costs, including the mortgage payment, property taxes, insurance, maintenance, and vacancy allowance, since monthly rental prices might range from $1,000 to $1,600.Property Appreciation: Take into account the market's expected and past rates of property appreciation.

He is ONLY willing to sell by owner financing.I am not a tax expert in estate taxes, but my guess from knowing others who have had similar situations is that IF he sold it outright for say 300K, he might have 75K of taxes.