If you're just doing some mailers and flyers, you merely need any old desktop publishing program. Heck, you can get most of what you need done in most word processors, and a dedicated desktop publisher isn't necessarily needed.

My go-to apps, back when I did desktop publishing professionally, were PageMaker and Corel Draw. Shows you how long ago I did it. :-)

My most recent encounter with desktop publishing was when I needed to make an album cover, and for that I just used Microsoft Publisher, because I already had access to a regular license for Microsoft Office. You might already have that license too? Though there were parts of it that made me wish for PageMaker again, I was still able to get done what I needed to get done with Publisher.