The question is not specific enough to give a complete answer.
How large is the lawn, is it flat or hilly many flower bed's or trees are factors.
The next question is how much do you want to spend? There is some relationship between price and quality, but frankly not much.
Do you want to mulch or bag is another question to consider.
Then on the uncomfortable side, are you a light weight or on the heavy side, that sort of matters when you look at the size of engine.
Now that I have given you things to consider, go to Sears. There garden tractors are made by American Yard Products who also produces under a variety of labels. A quality product, you can always get parts and service and remember the objective is to cut the lawn.
Hope this helps.