Rebel is not totally correct.
The US company will have to register in the DR (neither cheap nor easy), will have to file timely labor and payroll reports, pay all labor costs (social insurance, etc.) and will be liable for all Dominican labor laws.
You do get a US tax exclusion for income earned offshore, but you will have to file Dominican Income Taxes and pay on income earned above RD$25000 (I think that's the amount; could be a little more or less) per month, about US$500 per month.
And when you file US taxes as a foreign resudent, you have numerous additional forms you have to file to make sure you are not holding money offshore Uncle Sam thinks may be his.
It's not as simple to become 100% legal in the DR as one may think.
The DR is a very difficult business environment.
Then again, you could just do what many do: don't do anything, go legally commando, and hope you don't get caught.
I have my own LLC in florida and I am living in DR and in US less than 30 days out of the year. My income is earned with customers in the united states. Just the fact that I am not living in the US more than 30 days is that enough to get the exclusing of 100 grand a year to not pay taxes?