Making offer on unlisted property

[Rich C.]

I recently contacted the owner of a quadruplex that I am interested in. The owner is a realtor and suggested to make an offer to see if we are in the right ballpark. They don't need to sell. This is located in a great area that has transitioned over the last few years. I know the owner got the property at a steal and that the current tenants are from before the neighborhood transitioned. Thus, my intention is to renovate and charge new tenants market rents.

-I am not necessarily concerned with current rent roll because I know what market rents are, although could be a negotiating tool
-I don't know the condition of the inside yet
-I have a general idea of what the monthly expenses after reno will be
-There is a strong comp from 5 months ago up the street that seems to be in better condition and is what I would be basing an offer off of

I am trying to figure out how to approach making an offer and responding back.

Options:
-Ask for all of the income amounts and request to see the property
-Not waste everyone's time by making a ballpark offer based on the comp up the street and then make any adjustments if the inspection and viewing of the property is in worse condition

Any suggestions would be helpful.