Yes, the rental income can be used again depending on how the rental/commercial lease is structured.It would make sense to to these two deals simultaneously that is if your wanting to convert form FHA to conventioanl and remove the MIP - monthly insurance premium. 

Long story short, i'm currently in 24, living in Charlotte NC and looking to buy my first home to rent out to a tenant to help pay down the mortgage while I simultaneously build equity in the home so in a year or so I can take out a HELOC and use that as a down payment on my next home.I've applied to get pre approval from a few lenders and i'm running into some issues.

These things can all happen simultaneously, and in a sense this research and due diligence should be on-going.

Is this SIMULTANEOUS or if the first is pending a refi/pay off?

Simultaneously start attending local real estate meetups. 

How can it be both simultaneously?  

@Courtney Kelly it's called dual agency and it is allowed, however, I don't see how the agent can effectively represent both parties simultaneously. 

HI Irving,You can use FHA to purchase however just note that if you do use FHA and you simultanously are vacating (leaving) your current primary residence that you might not be able to use a lease or rental income to help offset your property's payment to qualify for the new FHA upleg property.This rule is commonly referred to as the 100 mile rule and the premise of the rule is that FHA wont let you use rental income offset if the new property is under 100 miles away from your current primary (unelss if you're employer relocates you).

If I were in your situation, I would make one May 1 and one June 1 so that if both leave in the future, I don't have to fix, clean, and fill both apartments simultaneously. 

My management company uses software that allows us to list on both sites simultaneously and maximize earning potential through both platforms.