New to investing and my first property is a triplex in Alamogordo NM that I bought from a friend for $50k(seller finance) who wants out of the real estate business.

However, when I reached out, it was a personal seller.

I do have concerns about the risk but does it *ever* make sense for a seller to enter into this sort of agreement?

Neither.All these damn weird letters with scribbles and red fort black font, green font is all rubbish.A seller is not some mystical creature you know nothing about. 

Its not like hard collateral which is how I am wondering how it is factored into the demand for the investment on comparison to real estate.

@Finian ButcherAsk for a signed receipt from seller that they received your offer.

One important item of a good answer would be knowing your goals  If the answer of yours is that these are on a short term investment I would tell you to sell both units if it is a hot area and is a sellers market there I would probably say to sell both of them as soon as possible if the seller's market continues and I might not spend your own or borrowed money before you sale.  

If not, does anyone have any suggestions on how to handle it with the seller?  

My current situation is that I have a seller who countered me and the price they are asking would make a meh deal.

Overall, assuming there is enough demand to meet these numbers and we can buy at these still very depressed prices, it seems like it would be a low floor and low maintenance investment, generate moderate returns for the next 5-10 years, and have very high potential ceiling in the event the area experiences a comeback which many special interests are already working towards.