Hi John, keeping your current house because you have 'equity now' and probably a great rate on the existing financing is not a great investment philosophy. If your goal is for this to be your gateway into becoming an investor, which a lot of people do, it usually crashes and burns. I would sit down and crunch the numbers on what it looks like to try and pull this off, if you even qualify, and different scenarios for example, second home financing vs. HELOC. HELOCs are the ones effected mostly by the FED jacking up the fed funds rate and are not locked in so that could spell disaster.
Maybe the best play is to cash out, buy your bigger home with out worries and keep some of the money to buy your first investment property in the next 6 months when you can find a great opportunity to buy below market, and maybe use creative financing to hit your mark.
Point being, make a plan, use strict criteria and work for it. What is your 5 year goal, 10 year... etc. If you don't know, figure that out first then work backwards.