Step 1: Go to CreditKarma.com and set up free monitoring account
Step 2: Go to your bank and order a secured credit card in the amount of $300
Step 3: Start using it to pay for gas. Never spend over 30% and pay off the amount as soon as the balance hits so you're never charged interest. (I did this and it raised my scored about 10 points every month).
Step 4: Get 1 more secured cards for the same amount and repeat.
Step 5: Repeat process. (so you have 3 lines of revolving credit). Again use them only for everyday purchases and never go over 30%
Step 5: Write to the credit bureaus to remove negative inquiries off your credit. Creditors only have X number of days to respond. If they don't then it has to be removed.
Step 6: Call a loan officer. Have them run your credit and look at your numbers. Your debt to income ratio will need to be under 43% to qualify for a QM loan product. Talk with them about various loan programs and see which is the best fit for you. There are several low down payment programs available and many times family member can gift your down payment should you need some help there.
Step 7: Create a saving schedule & debt reduction plan. This may require talking to a specialist but you might be able to do this on your own with proper research and planning.
Best of luck!