I think there’s some sort of option of to do a little refi on both house 1 and 2 and get the money needed to wipe out the line of credit(allowing for bigger flip opportunities, especially if I partner up with someone) and also renovating that garage space with the private investor as long as it is under 1000/month.

On the positive side, the price points and rent-to-price ratios in Detroit make it a compelling option compared to California.

Just be sure it’s documented and consistently applied to avoid any Fair Housing pitfalls.Another option is to stick with strictly quantifiable criteria—credit score, income ratio, etc.

Cash for keys is a good option but it depends how much they owe.

If not, they may want to speak to a mortgage broker local here in Florida to help expand their options! 

That really isn't good enough in our opinion.Another option for you is if your property is in a realtively safe area, to install a wi-fi connected smart lock.

With the newer 5% down conventional loan for owner-occupied multifamily option, I generally advise people to start analyzing from there if they want to house hack a multifamily with minimal down.  

Cashing out $400k and throwing it in an index fund is a viable option as well.

That is an easy list to build and a much better and safer option than more creative like Sub To.

I look forward to your response and the opportunity to discuss potential options that align with your organization's leasing policies."