I really have no problems Installing doors from home stores like The Home Depot or Lowes and to be honest I buy from them myself when I need a basic stock item.
Not only do the home stores have a fair selection of commonly used doors but their quality is equal to those from other door specialty suppliers.
The prices from the Home Depot and Lowes cannot be beat unless you're ordering a special door and then it's far better to order from someone else because they charge a premium once the "special order" forms come out.
I find that buying basic interior doors that I am going to Install into a customers existing door frames can not only save a few dollars but also I can get them without hassle however the styles are limited to what's popular.
I also find that the most common doors that I purchase from The Home Depot are pre-hung Steel or Fiberglass doors that I would be using on the side or rear of a garage where wood doors simply don't last and as long as theyre painted correctly they'll last a long time.
So, before spending a small fortune on a basic door let me first took to one of these great home stores and please keep in mind that I will even pick up a door from a local store that you have picked out, bought and put in will-call and I wont charge for this service whereas they'll charge around $65.00 to deliver it for you.