Used is a good way to get more gun for less money, especially models that have been replaced. One caution with ML's unlike CF's is care and attention, as BP and sub powders are corrosive and attract moisture more so then smokeless powder used in CF's. When assessing a used ML, don't just look at the outside and inside of bore, check breach area, if removal breech check breach plug and thread and if possible remove stock/action to see if any major issues are hidding. Like a cf check the crown rifling to ensure good grooves still exist, aka barrel not shot out. ML's round out faster then cf due to ramrods needed to load projectiles.
Not really up on the budget new ML's these days so can't really help you too much in that regard. Like mentioned the BP forum would be a great place to post this thread.