need help with commercial investment calculation

[Amy Park]

I have an option to purchase three commercial condo units in a professional building for $325,000 from the owner finance, with 15% down payment, at 5% interest for 10 years. The rent from current tenants are at $2150/month for two units and I will use the smallest unit that is vacant for my private practice. Because it is a condo, I will have HOA for all three units, insurance, and tax ($900/month for all three). The smallest unit(A) that I will use is on sale for $70,000. Unit B is for $90,000(rent income $875) unit C is 165,000(rent $1250). I would appreciate some advice as to the investment value for all three units versus 2 versus one unit. thank you everyone!