Seller Wants an Offer Before Seeing Property

[Elton Tate]

My wife and I are currently looking into investing in Detroit and have secured the pre-approval letter. Upon looking for a home to invest in, we noticed the seller only allows us to see the property if an offer is made. Is this normal? Also, when asked about current lease agreements and rent rolls, no one responded. Is this weird? All properties are tenant-occupied and pay rent at or above the market rate. This practice is very odd to me. It even happens for homes with no tenants.