If I sell them the capital gains, agent fees, and depreciation recapture will take a large chunk of the profits plus I need to pay off the remaining mortgages. 

I would then put up the cost of the repairs and take the remaining profit for the next investment.Has anyone done a deal like this in the past?

This concludes scenario B.We have spoken about both of our situations, and my mother is looking into selling her home and taking whatever profits she can make out of this sale and making a lumpsum payment towards MY townhome’s mortgage (which has about 59k remaining.)1.)

Purchase price (estimate): $370,000Rehab: $80,000 (ultimately two of the eight units have been recently remodeled, but the remaining six units will need cosmetic updates.

You can always have a local agent put you into an MLS portal that is directly tied in.  

I wrote an article about this a while back you might find helpful: https://www.biggerpockets.com/...It references an old study from the 90s, but I think it's still more or less true and a good starting point for this discussion: In 2003, the National Association of Realtors came out with a study on the characteristics that increase and decrease the price of new housing (assuming all other characteristics, i.e. square footage, remain the same).

From my experience, waterfront properties are closely tied to the current economy and their prices fluctuate accordingly.

If he sells out from under you, he still gets the money less any remaining principal and still only pays 15% long term capitals gains tax (on the profit/gain).  

I have enough money to buy a property in cash ($140,000), but the problem I foresee is that my capital will all be tied up in equity.

Their reportable income is low and most of their net worth is tied up in their share of their business.