re: Best bang for buck push mower

Tree roots, if tall enough are a good way to bend the crankshaft, or possibly split the engine case if the blade hits them hard enough.

You'll at least need to get a mower with quick height adjusting wheels to try to avoid the roots.

I picked up a 22 inch TroyBilt mower with a 140cc engine from Home Depot last year for under $250 and it replaced one similar to it that lasted me almost 13 years until the body rusted out enough to make it not safe to use.