They take application and collect documents submitting to an underwriter who then determines loan qualifications.  

@Kyle Griffin You need to be employed for 2 yrs consistently in a similar job to use the income for loan qualification.

For instance I know of many 're investors' whose only 'investment' in real estate has been reasearch and throwing around offers with apparently never one account of having owned, sold, wholesaled, or legally otherwise invested in real property.In other words, it's overall a non-issue as far as qualification.

I carry applications with me along with a flyer stating renter qualifications, background checks, security deposit amounts, etc.

Of course it could mean finding the perfect tenant who didn't apply before because of income qualification.

Getting a pre-qualification letter is very fast and easy, and it will give you a very good idea whether you will be approved or not, just give true numbers.Pre approval takes more time but it positions you better at the eyes of the seller and the agent if you are going to buy through a realtor. 

The FHA identifies the following benefits: Low cost -- FHA-insured loans have competitive interest rates because the federal government insures the loans for lenders.Smaller down payment -- FHA-insured loans have a low 3.5% down payment and the money can come from a family member, employer or charitable organization as a gift.Easier qualification -- Because FHA insures your mortgage, lenders may be more willing to give you loan terms that make it easier for you to qualify.Less than perfect credit -- You don't have to have perfect credit to get an FHA-insured mortgage.

Sometimes it's not up to what the buyer thinks, estate matters, medical qualification audits for assistance, bankruptcy, sometimes the buyer can love you and still be required to act in their best interests.

I started working with some agent for refi and i might be able to get pre qualification. 

Services have wide variables, expertise, knowledge, qualifications, level of services offered.