Prices in other posts sound right, but depends on condition. I repaired a rusted deck on one, then got a new one. A rear discharge works better, spreads the clippings out more. The better mowers have a fairly thick deck and will cut faster due IMO to the heavy deck keeping down vibration. Wheels at all 4 corners are necessary to keep from scalping. A roller in the middle front keeps down the scalping too. They cut better if the rpms are kept up high. A 6 foot mower is better so that you are cutting over the tractor tracks.
Sharp blades are a must. An air wrench is required to break loose the blade nuts. I never could figure a way to hold the blades and loosen with a wrench. Be careful getting under the deck.
Keep the belt tight. A little bit of slipping and you need a new belt.
A zero turn mower will cut rings around a finish mower, but you have to pay serious money for a good ZTR, and I don't think a cheap one is worth having.
A finish mower is not a bush hog, they don't like tree sprouts.