Background check can be performed in-house by your own staff or it can be outsourced to a tenant screening company. Most landlords and property managers do both: outsourcing the credit report to a tenant screening company and doing the verification process themselves.
When performing the Personal Background Check it is important to keep good notes and to treat every applicant the same. If you do a different type of background check on different applicants, you could find yourselves in trouble with Fair Housing law. Fair Housing is stern that when performing a background check that every applicant is treated using the same evaluation methods.