re: Zero-turn mower rec. - 4K or less

1) Residential grade will be rated for less hours.

Some mfg fool the avg mouth breather which not hard by putting a lot of weight heavy welded deck and have small engine push it. Those units like entry level hustler and bad boys come in the shop left and right for transmission usually by the second year. Heat and weight on a sealed EZT transmission do not mix.

2) transmission sealed Hydro gear EZT unit.
Builds up heat more.
ZT- series you know the difference have plastic fill pod and have oil filters on each side.
Typically see double the life of a residential unit.

Engine some might be a step up most residential do put a cast iron sleeve engine on the units. Gives cylinder wall strength so that tit for tat.

Basically paying for transmission and better seat in most units with little bigger engine to push the transmission.