Buying a house on low income?

My boyfriend wants to buy a 143,000 dollar house. While i will be assisting on costs, since im not going on the deed for the home, my income is irrelevant. He makes 12.50 as an hvac technician and is expecting a big bump near the end of the year. My question is, with an average credit score, and lower income can anyone apply for a mortgage? Or if its an easier question, how can you NOT be eligible to qualify for one? He meets with a credit company tomorrow who are great with stuff like this, i was just wondering if anyone else bought a house on low income.

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