Can I Convert Detached Garage to ADU with an FHA Loan?

[Stephanie Math]

Hello! First time posting, first time home-buyer.

I have an approval and am currently in the process of contracting a single-family dwelling with an FHA loan. I am located in Virginia. There is a detached garage on the property; it has plumbing and electricity. Both will need to be updated. It does not have a kitchen. No heating source. It is in "disrepair" and needs some work.

My plan is to get the detached garage fixed up and rent it out - long-term (30+ days). Does anyone know if this is allowed with an FHA loan? I do not care about having that rent count as income - I do not need that. I just want the extra cash to put towards my mortgage. I've read the HUD handbook for FHA loans, but can't discern if it is actually permissible. It says that rental income on the subject property can count towards my income, so that must mean that I can have the actual unit. Correct? This may seem obvious, but I do not want to shoot myself in the foot.

Thanks!