It's great that you're looking into owning, it's much cheaper than Renting here in Buffalo NY, especially if you bought a double, live in one unit and rent the other...then you'd be living for free...in some cases, maybe earn cash flow.
Without credit, you can't get a loan from the bank. There are creative financing that some people in your situation have used. For $15,000 house, you do have 1/3 saved, it may be best to continue saving.
And to start building up your credit, you should open a credit card account...I'd be happy to share more options and things to look out for. Please don't hesitate to contact me.
Congratulations on graduation, finding a good job and saving some money. Chances are you do have some credit, a cell phone, student loan, utility bill etc. If the home only costs $15,000 you have 1/3 down and may be able to obtain owner financing. If you meant the home is $150,000 I would start with a mortgage broker or your local bank or credit union. FHA requires 3.5% down payment, so you are close at the asking price. Find an agent to represent you and see if you can get a better deal.