This is how I met my first clients and now a lot of my businesses is Repeat business.    

It would be nice if you gave them more than that, because it takes a lot of effort to move a business (online marketing, business cards, etc.).

Several options you can explore to get the down payment capital: Solo401k; HELOC on personal residence or from equity of the SFR; Cash Value Life Insurance Policy; Business Credit; Private Lenders, to name a few.

Quote from @Byram Heights: You shouldn't be in this business!

However, if you're a W2 high income earner or business owner, I can't imagine it makes any sense to flip houses, mail mass post cards, wholesale, or build lead gen websites with the value of your time being better spent other places (such as learning about real estate and increasing your income through proven means), such as at your 9-5pm or growing your business, and your real estate is a long term process and you don't need "home run" deals to qualify or make it work.

I would look up NARPM and start with them..Below are some questions I would think would be a good starting point for you to see who really treats their company like a business or a hobby.

Treasury predicts 32,000,000 businesses will now have to comply with these new laws starting in 2024!

Quote from @Jonathan Grzeszczyk: David Greene has a series (Sold, Skilled, Scale) that teaches agents how to run their business like a business.

As in any area of real estate investing, it's best to know your niche and the areas you're wanting to do business in.

In my experience, the good ones are expensive, typically require a subscription, and sometimes they even do a physical inspection of your premises to verify it is a legitimate person / business in US.