OK, Punta Cana and the Capital are worlds apart, not only in distance but in everything else, people, living, costs, everything.
Have you visited the capital? probably an idea before deciding you want to live here, it is not the Caribbean you know from vacation.
Jobs? Call centre is the only option unless you have a degree, TEFL certificate and a couple of years experience, then you can make sh1t money working in a school.
Call centres will pay you 100pesos per hour, you will work about 8 or 9 hours a day and get paid for 7, you will be promised the transport home to save on travel costs and late night problems in the street but it will rarely turn up. You will work 5 or 6 days a week, and you must work one of the weekend days. usually calling the states and so take the working hours into consideration and you are in the office the best part of the day. So you will take home around 14000 to 16000 pesos per month, depends on who you work for, you have no right to be paid here and so they can and will deduct what they want from your salary and call it emergency tax, you will be paid the wage after 1 month, you will not get paid when you leave.
Living, young white girl needs to be in a safe environment, studio apartment furnished will cost you around 15-20,000 pesos per month, possibly need to pay bills, lecy, 1200pesos +or- per month, internet, 1000pesos +or-.
Unfurnished you can get a place for around 10,000 pesos, you will need to buy an inverter, varying costs but can be very expensive, fridge 20,000, sofa 20,000, oven/stove 14,000, bed 14,000, matress 17,000. Cieling fans 4,000 each, fixings and odds n sods 10,000, microwave 4,000, TV 20,000, hi-fi 10,000. Kitchen stuff, use your imagination, linen and towels 7000 +.
That might be a basic set up on a cheap scale shop, you know there is another 30,000 at least of homely stuff to go on that and still no where near a complete homely home.
rent is paid on a 6 month minimum usually 12 month contract with 2 or 3 months upfront (3 if you use and agent, 2 if you go direct) and then 1 month in advance.
Hope this helps.