They just need to be able to demonstrate it.There are also limits on how much gift money you can use depending on if its a primary residence versus a second home.You can use a collateralized loan backed by physical assets or stocks or bonds for the downpayment.

@Joseph Falco congrats, you have completed the first step to having a million dollars in the stock market.  

Investors behind you could mitigate risk as well.I am in no way predicting another GFC  but I saw a lot of large landlords lose their entire portfolios because vacancy hit 20 to 25% and stayed there and some even much higher... 

All the money I have saved is either invested in small-cap stock or has been set aside for this.

I still like to look for undervalued stocks while saving up for my next rental.

Next is to take stock of your goals (for example, accumulate wealth for retirement, quit your job, etc) and be able to articulate them clearly.

It's been only a few months since I joined bpand already reaping the benefits by getting new insights in to real estate from experienced members.I wish there was a similar platform for stock market as well appreciate if someone can share such a platform (if any) for stocks.

However, I have $5000 right now and plan on investing in stocks for four years, and then buy a duplex/triplex wherever I get stationed.But afterwards, could it be possible to take out a $3 million loan?

Doesn’t matter is the assets are cash, stock, real estate, gold or quite honestly even your car!

I've used Capital One and Discover along with a HELOC.Also, it kind of depends on where the stock market is at.