A piece of advice that many Peace Corps volunteers gave me (it was useful too) is that if you're not having good luck with the apartments listed in the paper, you should go to a neighborhood that you would like to live in (for $400 U.S., you could live in a nicer neighborhood of Santo Domingo) and ask at the neighborhood colmado if anyone is renting anything in that neighborhood, or if they know who you could talk to. It also helped me to have a Dominican friend with me when I was looking for apartments, because it kept them from giving me an outlandish gringa "discount". I'm sure I still got a "discount", but the prices that people were telling me (or the weird charges that they were adding on to the rent price listed in advertisements) were not nearly as high (or the charges didn't exist) when I was with a Dominican. Good luck, and I know that you'll find something great. Just don't rush through it, be VERY patient, and it will work out.