After rehab, expected rental profit after expenses (not including holding or maintenance cost) would be $600/month.I am new to real estate investment and while the cash flow would be good, it is prohibitively far and an undesirable neighborhood. 

Hopefully you will find a good tenant at your asking price, it's certainly possible as it's a nice house and demand is very high in the whole metro area, even spilling over into previously undesirable areas, however I think you're a bit overpriced for that immediate area at this time.

i've been looking in different areas around miami but either it's too expensive or the property is just in a pretty undesirable neighborhood OR it's in real bad condition.

They become run down quickly because the people living there either do not have the money to spend to fix them up or spend that money on other things (whatever those things may be).You propose to build a substandard size less desirable structure than the surrounding area, which seems to indicate  (based on other similar price points) that it will quickly become one of the most undesirable places to live in that area due to High Violent Crime.

Although, that statement is not entirely true because a $2 million home on an ocean from property will (most-often - hopefully) increase in value many more times than 10 dumps in an undesirable neighborhood.

I coach the undesirables and some of those being sex offenders.

Is that area more undesirable since there is more vacant properties in that zip code than cash buyers ?

I'm sorry have to move for undesirable circumstances but I love that you have a plan and despite what's going on you aren't getting deterred.

or its undesirable to you too? 

@Michael Bridgett FHA is just as undesirable as VA.