The leases that I've been involved with for the feds are very specific as to what they will and won't pay, what is needed in the space,; and, most of the leases are gross leases wherein the Landlord has to calculate many unknowns.

You need to start by determining what your annual gross income potential is. 

And I have done them , its rather gross . 

It means it should NOT exceed non-section 8 comps gross rent.

When you say $400-$600 per door, is that Gross (before CapEx, Maint, Utilities etc) or NET? 

I've noticed that in Miami, gross rental yields can reach 10%, with greater legal certainty and just an 8-hour direct flight from Madrid.My plan is to enter the Miami real estate market in cash, demanding a good discount.

I've always calculated NOI as gross income minus operating expenses (not debt or cap ex) period. 

Using 15% of gross rent to cover maintenance, capex and vacancies and you're left with $475.

Based on my research so far, Atlanta seems to be one of the places with a favorable gross rental multiplier, good prospect for appreciation, and sales price around the budget I am looking for and hence I chose Atlanta.

Can you give us idea of gross expenses and income?