In reading as much as I can about marketing I have determined that I might be better off concentrating on specific zip codes with more letters per property.

I don't think it's good to rule the first three out completely, but if you are trying to further your dollar, and your time, concentrate on those individuals you feel are motivated and not making the effort to call you.

In that case which 'groups' should I concentrate on?

I would concentrate in the area of high equity properties and also htose with major repairs needed as most investors like the ARV model.

That is about 1 dollar apiece.Should be 50 cents if you do yourself.If you have limited funds don't start out at 200.Do a more concentrated and highly targeted approach.It's better to send 100 letters to quality prospects than 1,000 letters to the wrong audience.

We can do, have, and be exactly what we wish.Tony RobbinsInspirational, Change, WishOne reason so few of us achieve what we truly want is that we never direct our focus; we never concentrate our power.

I do have to agree (which you will hear a lot around here) with @Joel Owens - Get focused, find your niche and concentrate on that to start with.Good Luck - And yes,  Thank you for your Service!  

And an area which will provide a nice cashflow with my budget.I have done abit of research on my end but i keep skipping from cities to cities not knowing where i should concentrate on.

sounds like you are asking a dolphin to climb a tree and wondering why it can't.You have a non-warrantable condo with a serious investor concentration problem, the condo itself may be a dog being a 1/1, with that many investors, the HOA may be in trouble financially and it may be a bit run down affecting value.A local bank and most brokers will not be able to get this done.  

People spend too much time concentrating on entities; websites; etc. versus finding their first deal.