Does anyone know how to finance a single family house that already has an assisted living company running a business in it? 

There are a good amount of single family/ residential homes in that area.

BP family, I just purchased a home through seller financing.

We want to buy a multi family of 2-3 units and house hack by living in one and renting out the other one or two units.

Happy to help you connect with contractors my family has used and that I know of personally. 

I'm agent in  kentucky and california, finding a deal between 7%-10% in single family residential in louisville, Ky is the norm, in california you can expect closer to 3%-4%. 

Lately, I've been torn between investing in multifamily or single-family properties.

There are also a couple boarding schools and private schools in the area that bring in wealthier families for visits. 

what I was thinking I can do is move my family into the empty unit after the lease is up and attempt to furnish the unit I live in currently ...

Explained the situation and he said it may be a challenge to get another conventional loan (investment loan is being considered as well but; Family loan = plan A, bank loan = plan B).We want to keep the property we live in now (since Oct 2023) and rent it out when we leave.