BRRRR with Pre Existing Tenant in Place

I am looking at a deal that is off market and I found it through mailing. The owner owns a few rentals and is on the older side. The house is 2/1 864 sqft. The outside looks like it could use a paint job.It has a new roof, updated mechanicals and a tenant that has been there 7 years and pays on time. Rent is $650. Taxes are currently $614 but I put $714 in calculator. I am getting a quote now on home insurance but the area runs about $50 a month on a house that size. The owner is asking $44,000 and my ARV using Zillow closed sales this year show it to be around $62,208 using price per sqft. When I spoke with the owner I asked if he would do seller financing and he said he would do a land contract $7000 down with three year balloon. I have never done a BRRRR deal or seller financing deal. I wanted to get advice on how to run this deal. Do I do it as a BRRRR in which case I am not sure what to do with a good tenant or just a straight rental?