Some kinds of auctions allow you similar protections as a traditional sale.

For the ballon payment I would plan to refinance into a traditional 30 year loan.

From the sentiment of your post it seems like you're viewing the buyers as strictly investors when they may lean more towards traditional homeowners looking for a quality of life improvement or an improvement on their current financial situation today.Let's say the buyer pays 465k and has a 5% interest rate.

Traditional mortgage?

I’m currently evaluating whether to go with a Fund Model instead of a traditional JV for an upcoming multifamily project, I will be working as a developer looking to do work with a more experienced developer on a larger scale multi-family opportunity.

That can hurt your cash flow and could equate to the same as a traditional long term hold without the headache and management.I'm not saying don't do it, I'm saying you have to look at all options. 

Buying properties through non traditional channels.  4.

I have used both Traditional (pre-tax) funds, Roth and HSA.

The reason sellers cannot sell these properties through the traditional market is often due to certain issues, and 98% of the time, these issues are not beneficial to you as a buyer.

Traditional mortgage from a big bank, 10% down payment What was the outcome?