Our options are to put the money the stock market, buy a multi-unit property, by an established business, payoff the 3 rentals for cash flow, or get into hard money lending.

Essentially are you cash flow positive or negative each month?

Since you prioritize appreciation over cash flow, focus on DFW areas with strong job growth, infrastructure investment, and limited housing supply—such as Frisco, Arlington, and Rockwall.

Yes not just for cash flow but for the health of the deal.

I think it is fair to say that there is somewhat of a tradeoff between markets that provide positive cash flow on day one and relatively high appreciation-based markets.

Raising money is all about marketing and sales (not real estate specific) so either hire marketing agency and read sales books, or hop on some LinkedIn courses on marketing and sales.Not sure the legal structure to use: talk to accountants and attorneys.Need deal flow: talk to brokers and go to a lot of networking events.Lending terms: start calling banks and loan brokers.From there, it is all risk mitigation. 

If you know where to look and have the right time, you can find properties that cash flow.

One month vacancy can eat up all the cash flow.

You may also have to get your "hands dirty" in order to make these properties cash flow.

Now, this would obviously be negatively cash flowing since you would need to pay taxes and insurance.