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).

Yes, there are ITIN DSCR lenders out here for $100K and up DSCR loans.More info on DSCR loans:DSCR loans won't use your income to underwrite the loan.

I live in Garden City, Missouri, which is about 45 minutes drive from the property in Kansas City.The property is currently vacant.I own the home, have no loans or mortgages.

Then what would the loan amount on the home be at that point?

You will get appreciation, loan amortization, and housing expense savings while you're there. 

I want to house hack the next 4plex with a conventional primary loan using 5% down. 

I know I will have to put down at least 20% with an FHA loan.

I was told my by loan offer over a year ago that the rates in spring of 2024 would be back in the low 6's high 5's... look where we are. 

Can I use an fha loan for a multi family property new construction?

- A traditional investment loan down payment of 25% down is doable but still hard to cash flow.