Should be no more than 43% for FHA. 36% for Conventional.And, you have to have the down payment, closing costs, and reserves.Since you're looking at a duplex using FHA.

We are selling one of our duplexes located in Portsmouth. 

My biggest advice is to do any major demo and work (taking out a wall, replacing/repainting cabinets, refinishing or replacing floors).

I plan on using a VA Home Loan to purchas a duplex in my local area that I will then move myself, wife and two kids into. 

I would be willing to self manage if I find a duplex property close enough to me, otherwise I would look more at having a property manager.I'd love to talk more with you about real estate some time. 

But now with the amount I do have left over from that sale (about 20K), and no debt, I figured I should start off with a single family home or a duplex out-of-state.

Expect to have some wall cracking and maybe even a structural issue to deal with.

I would like to buy a owner occupied Duplex, Triplex, or Fourplex as my first property. 

I was contacted by a potential seller, him and his wife are still on the deed of a duplex.

So that's a difference in itself from previous properties.For the record, I do not miss self-managing my duplexes.