Owner Occupied Duplex needing to buy out another family member

[Matt Halls]

My mom lives in my grandparents house. It’s a duplex that is in her name. She needs to buy out my aunt and potentially my uncle. The house was appraised by a realtor friend of mine at 258,000. My mom is disabled and income is very limited. The other side of the duplex currently rents for 750. It’s under market but the tenant has been there for about 8-9 years. Thinking that we can raise it gradually but trying to think about how we buy out my aunt. How do we value the property? I think 258 is nuts but it’s in a good school district and the taxes are low. Thinking this is the best way for my mom to have a place to stay vs with me. Any ideas? Assume her credit is not very good.