Preparing For Buy and Hold Rental Properties

I’m 15 years old and in this last year I’ve been hooked on commercial rental properties. How can I prepare to be ready to buy at 18?  Not only to establish credit, but too, my income to debt ratio is 0-0. I’ve managed to put Together savings, and have a growing assets in the stock exchange, but wouldn’t a underwriter want to see a stable pay stub? Of course I can get some job to compensate, but tell me what you think, 

All the best,

Owen