To me the solution is very simple.

Do as am.  I started  doing this back  in December.  It is a very good  weeding out  process. I asked for a  retainer.   Lawyers have done it for ever, so  why can't we ?

I simply explain  that even though I am sure THEY  would never   not pay  for my services, that unfortunately because   I have had a bad run of non- payers  it will necessary for me  to require  $ XXXXX  in advance.  Any  additional monies owed will be billed, and any over payment will be  credited to their account.  Just make sure you bill enough to cover  your time and expenses. That means  gas for your car too. This no mileage business is  nonsense. 

(Too many  of the companies   play the  poor card.  That is pure crap.  Their goal  is to get you  for as little as possible.  They always  blame it on their   client.  We can only  guess  what they  are billing. They  don't care what it cost you, just so they get the product. )

Yes,  I am getting work.  No, not as much, but  then I've cut out the dear  folks who  feel  no need to pay. All of my  work is now  productive for lack of a better term.

If we all  started this  policy the dead beats  would be out of business  in  very short order.

All my best  fellow title  searchers !

Larry