I brought this deal to a realtor i'd like to build a future relationship with.  

Surely your HOA has covenants and bylaws that cover these things, and if it doesn't then you should have some kind of relationship with legal counsel that can advise you of your rights in your state. 

Instead your time and energy should be focused on building solid relationships with realtors in your investing area.

We are in NC and we build relationships with brokers in our target markets who find us deals.

I would like to rent my house and we would live in his (plus children from previous relationships).

506(b) is quite common if you have a preexisting relationship with investors and do not need or want to publicly advertise. $150-250k is a pretty small raise for a syndication, though.

Trying to expand our options for properties and want to create a relationship with a lender that we can use for the future.

I can't seem to understand what is the relationship between solo 401k with social security at all.

So, that's what lead to me thinking about co-signing with either my sister or the investor I have been building a relationship with.

In either case, I find this behavior amongst agents extremely misleading and bordering on a breach of fiduciary relationship with their clients because it takes away a potentially higher sale number.