It also allows us to gain experience with managing rentals as it's built out and we don't have to go looking for deals to scale the initial portfolio. 

@Wendy Peterson, Well, you know that if the seller did a 1031 to purchase the property they are selling to you that there is probably a substantial amount of gain and tax to be paid if they don't take steps.Seller financing will trigger the gain and tax. 

If you sell for a profit, you pay taxes on the gains instead of letting those gains sit in place and grow long term.

Capital gains tax in RI is 6%, just saying.

After I explained that after a 6% commission, cap gains on the "investment property, income tax (to be reported by the son) that it would be more economical for them to sell it to me for $150K with no realtor.

I would nix the pet washing station and doggie poop bags, the cost doesn't justify the gain.   

I sold a property last year, fortunately I do not have to pay capital gains as It was my primary residence before being rented.

Since you are transferring basis into the new investment, that will limit your depreciation since the gain is excluded.

2) Capital Gains. 

I am debating whether to rent out the current unit I am living in (that has access to the backyard and pool) or sell the property and reinvest the gains into other projects.