What do people do about the return address?   Printed?  Handwritten?  None?

It depends on the mail piece.

Typically on YellowLetters it is typed on the back flap... We actually use envelope art on a lot of letters then we tuck the flap... Here is an example

You can also use a label to seal the envelope

And if a Number 10 and typically for a typed letter we will put a logo and address on the front typed and use either a handwritten font or human handwriting for the addressee. Something like...

I forgot to mention that if your using a Standard Stamp then you are required to use a return address or Indicia. On First Class you are not required to.

@Michael Q. Thanks for the insight.  I'm planning on typed letters per advice of @Sharon Vornholt  , would you put your personal name as in image or company name?  I'm trying to appear professional but not scare anyone off and of course make sure they open the letter!

I'd also love to hear Sharon's input on the above questions.  Thanks to you both.

For me it depends on which mailing it is. Some I use 1800Sell4Cash and some I use my name and some I dont do either. 

@Michael Q. Thank you.  Since I'm abusing you for the advice, I saw another thread today where you said no return addresses for yellow letters - is that just due to the difference in recipients?

Also, for probates, what do you do when you search for a person and you get multiple results for a common name?  Mail to all?

Mr Quarles answered this perfectly.  I learned some new stuff as well, thanks Mike!

I put the address of my UPS mailbox which looks like a regular address, and it is printed on the envelope. You can be yourself and still have a company name on your letterhead. Sorry for the late response.  I am on vacation.

Sharon