Does anyone know what I would pay capital gains on in MA? 

Difficulty in Financing: Selling a property purchased under a land contract can be more difficult, as potential buyers may be hesitant to take on the remaining payments.Benefits for Sellers: Deferred Capital Gains Tax: Sellers may be able to defer capital gains taxes on the sale of the property if certain conditions are met.

You will get a proration of the gain free according to the amount of time you lived in it versus the amount of time it was rented. 

Just a thought but I think this could be valuable to the right people.

(Yeah, that last one was a snarky comment.)CONSYou lose the homeowner capital gain exemption. 

Should I offer this guy a 5 year plan to help him save on capital gains?

There are some key limitations that are important:Passive losses can only offset passive income.Up to $25,000 in passive rental losses may be deducted against non-passive income if the investor actively participates and their modified adjusted gross income is below $100,000.Unused passive losses are carried forward to future tax years.Here’s an IRS article that further discusses the rules: https://www.irs.gov/publications/p9251031 ExchangesThis strategy allows investors to defer capital gains tax when they sell a property if they invest the sale proceeds into a “like-kind” property.

A couple of months ago, a screen popped up forcing me to pay a fee in order to gain access to my account.

I roughly calculated 50% of my gains came from appreciation and 50% from cash flow and mortgage payoff.  

But as you get better and gain experience, you typically see a 30% to 40% cancellation rate.