Hi Eric T,
First, a #4 or 41/2 are both smoothers, unless they have been modified as scrub planes. The #4s out number the 4 1/2s with the difference being that the 41/2s are wider planes. A #5 (Stanley numbering system) is what is normally referred to as a jack (as in “jack-of-all-trades” or, “jack knife” meaning something that is common). A jack can be used for rough work or super smoothing, just depending on how it is tuned and set up.
Like Bill says, your best bet is to always buy local when you can in order to save the shipping costs. Stanley made lots and lots of planes but unfortunately, they have gone through a period where the quality really went down hill. The pre-WWII planes have gotten a lot of attention but, in my opinion, the planes made through the early 1960’s can be just as good. and sometimes have heavier castings. The operative words are “can be”, because Stanley also made some cheaper, low end planes during the same period. Look for Stanley planes with all of the parts, no apparent damage, no plastic, frog adjustment screw, and the large brass depth adjustment wheel and you will pretty safe. Take the time, if you can, to take it apart to make sure there is plenty of blade left and there is no major pitting on the blade back since that can make the blade unusable. You can get replacement blades but that just adds to the final costs. Just remember that shine doesn’t necessarily make the tool work any better.
Estate sales, flea markets, and yard sales are normally your best bet and sometime they can be found at antique stores at reasonable prices. You should have no problem finding what you want within your budget.The problem most beginners have is telling a good one from a bad one and being able to tune them up so that they will perform well. I always encourage beginners to try and find a local experienced buddy, a woodworking group or to take a hand tool class if for no other reason than to find out just how well the tools can perform and how to fettle them if necessary. Barring that option, watch all of the videos you can on the subject.