Comps on Non-Typical Property

[Monica Litster]

I am looking at buying a property that is a 5 bed house with a 1 bed inlaw apt attached. Both are rented by long-term tenants. How do I find out an ARV or market value, because the regular channels for comps are not going to accommodate this type of structure. Does it become a square foot price scenario?

Thank you for your help.