It really depends. You're probably going to get a lower price on an off-market property for the simple fact that their are fewer people looking at it, but an off-market seller can be just as unrealistic as an on-market (MLS) seller.
Are you asking about short term rental properties?
no, buying ( and put the property for rent)
What is preventing your potential renters from buying the properties themselves, instead of renting it from you? Is there anything special or unique about your market? My town is the modern day equivalent of a Gold Rush town in the Wild West.