Just because you have had credit problems in the past doesn't necessarily mean that you are doomed to a life of dealing with landlords. Poor credit can be a result of people simply not paying their bills, or more uncontrollable circumstances such as illness. While lower FICOs (credit scores) do signify a higher credit risk, they do not mean future credit problems are certain. Because of that, there are possibilities for people with a low FICO to obtain a mortgage.
In lending there are terms that refer to the creditworthiness of a borrower. "Prime" is a term that indicates high credit scores, and solid financial footing. "Subprime" is a term that basically means "less than 'prime'." The term "subprime" has no relationship to the PRIME rate; this is commonly misunderstood.