@Nick Salemme - First of all, congrats on the purchase of your first property last year.
Everyone has a different strategy, different goals and different financial needs. Here are my thoughts:
1) Check with your accountant regarding the US Tax Code 121 capital gain exclusion. Once you move out of the property and it becomes a rental, I am not sure if the $250k/500k exclusion still applies.
2) Have you thought about purchasing multifamily properties (and house hacking) instead of single family properties at each step along the way? Each property would still be your primary residence so you should be able to get favorable financing. Plus you have tenants paying down your mortgage/rebuilding your cash reserves for the next purchase from day 1. Plus, you may be able to reach your goal of 4-5 rental units with 2-3 properties instead of 4-5.
3) Personally, unless the property makes no sense at all as a rental anymore, I am not a big fan of selling properties unless I have to. It costs 8-10% in closing costs between real estate commissions, NJ transfer taxes, legal fees, etc. Also, unless you are doing a 1031 exchange, there is likely a tax bill due (again check with your accountant). I prefer to pull 75-80% of the equity back out by either refinancing the mortgage or getting a line of credit against the property.