I wouldn't be able to cough up $400 that quickly and I'm single with no children or, even, pets to tend to!

Also the no pets policy may be hurting you just a bit especially if the unit has a yard. 

When we rented our place we asked for the first month's rent, 1000.00 security deposit and a non-refundable $500 pet fee, per pet.  

I charge a $300 pet fee (not a refundable pet deposit) and I do not charge any additional monthly rent for pets.

Some have pets that apartments won't allow. 

Pet peeve alert! 

Make sure they take their pets too.

I know I am not the only one who has a pet peeve with all these folks that come off as investors when they are really just salesmen.. but I think that is part fault of how BP operates you can't post on the forum side and market your wares you need to do that on Marketplace which gets 1/20th the traffic so you have of of course our lady friend in LA who says the exact same thing when she posts.. you have Joe doing it now.. another acquaintance of mine in Oregon is now doing it.. its just sublimanl marketing on the largest RE board in the world.. when I talk to many off line they finally figure it out and stop reading any of these peoples posts as they are all the same no real help just the.. same message.. ( I live in LA or the west coast and I only buy turn key)  then hope people talk with them then move right into sales mode.. but hey its emerica right .

I'd like to allow pets, but is it best to charge a pet deposit or up the rent a few bucks?

Treat it like an unpermitted pet or tenant not on the lease.