There are some restrictions and rules, all of which are detailed at the HUD website. There are no strict restrictions regarding income or the cost of the home, although it is helpful to demonstrate fiscal responsibility.
It depends on the house. Some houses are restricted to those who intend to reside in the house. Other listings are open to investors as well as those who want to make the home their primary residence. To buy a HUD home, you must work with a real estate agent.
You will need to ensure that your information is completely correct on your bid and you will need to ensure that you have proof of funds upon submitting the bid as the packet must be overnighted to them within 24 hours of acceptance.