I know I'm not bound by Fair Housing Laws with only 1 property, but it's something I want to be conscious of as I develop my process both for this go around and in the future.

If you are trying to convert a property under and hoa into an str, your job gets even more complicated as the HOA itself may have its own regulations IF it even accepts it at all.caution: STR market is over saturated in these parts and some of them are shuting down and being converted into corporate housing, mid term rentals, or furnished long term rentals.

I know here in San Diego I had to have permits just to put air conditioning into my house. 

They visited the house as part of their due diligence but I never heard anything further from them regarding any concerns they might have.  

I have equity in my property which is in Washington state, and I'm interested in finding an investor who would be interested in loaning me 20k to 30k in exchange for an agreed percentage rate when the house sells (within 10 years).

Land only and not houses.  

Motivation is to overcome down payment hurdle for expensive houses for STR

Besides private websites controlled by the brokerage houses themselves and the MLS, there isn't much left.

While MLS remains the primary platform for on-market deals, the majority of deals I encounter originate from off-market sources, often through wholesale channels.When you say wholesale, someone(wholesaler) finds a homeowner who is in need of cash quickly or cannot go through traditional process of selling their house for some reason, and then the wholesaler finds an investor to buy the house who will pay in cash? 

My original plan was to rent out the space to Section 8 tenants, but from my experience so far, dealing with Baltimore City housing and inspections can be a serious pill.