The notable exception is if you buy at the top of the market and need to sell at the bottom, but that is why you need a "margin of safety" in the form of excess equity created by a "killer deal" to insulate you from the short term market fluctuations.

In Florida for example, MHP tenants (when > 50% are Tenant Owned) can vote that a rent increase is excessive and take action to keep them lower.Looks like you've got your bases covered for the most part.

Still, <5% per year in taxes does seem somewhat excessive. 

That way your excess income on capital gains could go back into it as a contribution.

Everybody talks about and warns about the due on sales clause which is in just about every mortgage these days but never in all my years have I or anyone I have heard of had a lender actually excessive that clause so long as the payments were made on time every month.The seller has to be willing to agree to have his or her credit at risk in the event you the purchaser fail to make a payment which is why a third party loan services should be made as part of the contract and serviceing of the loan.That all said, a red flag pops out at me as to why this “gentleman” had this opportunity fall in his lap and wants nothing for it.

If repair cost is excessively high such that there isn't sufficient margin between ARV and total ownership cost (repair, acquisition etc.), that can be risky.

A great listing photo will be clear of excess stuff to make the property look bigger.The question as to whether or not you should keep the tenants in or do it after they have left is price point.

Any future property I buy (down payment comes from excess income on the quad) will be managed remotely by me (looking in same neighborhood) or I’m training my adult son to be a superintendent so I can have him live onsite and help me with the day-to-day management.

You want to be nice, but not excessive. 

Keep in mind that as long as he holds the real estate with the loan... he doesn’t pay any income tax on the excess proceeds.Layer that with a healthy developer fee and a number of other tax benefits related to zero cash flow and Section 467, and these deals wrote themselves.