Pre-screening can save you some time. However, I have found that a lot of people won't tell you about a disqualifying factor until you have shown them the unit. People probably think that they can "win you over" with their wonderfulness when you meet them in person. So often, even though I'll say "no pets" or "no pets over 25 lbs" someone will tell me that they have a very well behaved (funny how 99.9% of dogs are well behaved according to owners) labrador only after I've shown them the apartment.
I guess what I'm saying is that showing the apartment is part of the cost of doing business. One suggestion I would make is to post a video walk-through. That, along with the address, gives potential tenants a lot of information. When I do that, most tenants have already decided whether they're going to apply before I show it to them.
Whether you have to send a letter is based on state law, I believe. If you charge them a screening fee, you generally have to send them a letter.
One more thing, I don't publish a minimum credit score for acceptance. You may get an applicant with a 621 credit score with a lot of collection activity and other problems. By publishing a credit score, you might be boxing yourself in. I prefer to post something more general like.
"Acceptance is based on the following criteria
- Income: at least three times rent
- Criminal background
- Credit score and history
- Rental history including prior eviction "
BTW, of all of these, prior eviction is the #1 item for which I will instantly reject. Evictions are a ton of work for a landlord to complete. If the tenant has an eviction, some investor probably spent _months_ getting rid of the person. You don't want that.