Buyers are not very willing to cover the commission because they are use to no charge for the realtors services.

When using a Bank you need to be aware of the fees they charge. 

He gets 800 a month per bedroom for a 3 bedroom house but in reality for him to make money he needs to charge at least 3500-4000 per month in order to make money.

I'd make up for it by charging a higher per month rate, around $150-200 more/month. 

Was her application incomplete , did they get a good refrence from the previous landlord , do they make enough money ?    

However, I plan on just charging a move-in fee.

They must at least use the AFR ( applicable federal rate).

It's up to the tenant to ensure they have sufficient funds, if a Cozy payment fails or a check bounces I then charge the tenant a fee (assuming this causes it to be late).If you're really concerned you can take what @Jonathan Cope does one step further and require payments on, say, the 25th in your lease.

Being a mortgage broker we can't charge that much because it is illegal. 

Maybe I should have the manager bill the tenant for the water as it is part of the cleaning charge and necessary for the cleaning.