The best advice I can give is that you spend the next 3-6 months reading various threads here and listening to as many podcasts as you can.

I’d like to turn my primary residence - $225k townhouse (3 bed 2.5 bath) - into a rental and then go on and rent a $2500/month luxury townhouse.

The house will break even or profit about 100/month free and clear with about a 10% cash on cash return projected What I am considering / looking for advice:- can I owner finance a property if I have a mortgage on the unit?

Airbnb’s in this route are hot with some of them having 6 months of waitlist.Does anyone have any experience in short term rentals in Mexico?

You will end up losing the deal.You need about six months of networking and active deal flow to create a potential buyer's list and email distribution.However, if the deal is really good (very unlikely in New Jersey), it is true that you can find a buyer.

Plan is, ill pay Heloc in a year from what I save monthly. 

What is the best months to secure a property on the low end?

People have been waiting for interest rates to come down for 18+ months now.The reality is it will likely take longer than you expect to happen.

The investor generally needs 6 months of "reserves" or savings of mortgage, property taxes and insurance (and HOA if applicable).

I think I might go check out some of them in the next few months.