16 Unit apartment Building with 2 Bedroom rancher next door

[James Otto]

I came upon a deal of a senior couple looking to retire. There selling a 16 unit apartment complex with 2 bedroom rancher next door. My wife and I are interested in the apartment complex, and could care less about the house. The owners want to sell both together. There asking price is based on what the apartment complex GPR which is about 30% below market rents, and based on the potential that 2 more apartments "could be added" they also have there priced based on the ranch house rented out once they move out. What should we base our offer on? I was thinking to base the offer on the on the current value base one what there renting the apartments for. And make an offer only on the apartment complex, and if we want the house to buy that in a different contract. What do you guys think?

This is our first commerical property offer.