If my moms can creatively come up with a way to keep her taxable income below 47000$ ( for single filers) she would have to pay 0 in capital gains on the sale of her property, am i understanding this correctly. 

The Fair Housing Act (FHA) does apply to almost all housing types including those for sale or rent.

You're paying off the mortgage and giving the Seller some cash, so this is a normal sales transaction.

@Michael Nelson a refinance is an exit in a similar way that a sale would be and typically your note with your HML would stipulate that upon any sort of "exit" where another lender takes 1st position and owns the note or a seller buys it that they would need to be paid in full as the current 1st position lien holder.

For example, one triplex I have found is for sale at $140k and I estimate that it is worth at least $200k maybe even 250k.

I would explore accessing equity within the home or your rental prior to triggering a sale.

Have a lawyer draw up a sales agreement.

The property illicit great numbers (ROI, cash flow, sale price, etc.)

I travel to a lot of conferences all over the country on build to rent getting our product and name out there. 

Purchase price: $165,000 Cash invested: $182,000 Sale price: $215,000 https://www.zillow.com/homedetails/3960-N-Heatherhill-Dr-Memphis-TN-38135/42291251_zpid/Cleaned the property out, repaired roof, filled holes in drywall then relisted.