I've bought more lawn care gear than most. 34 years, new equipment every year, up to five vans. I've lost count of the mowers, line trimmers and blowers. Here's what I'd buy now, and the two rules I learned the hard way.
Whether you're buying for a small business or your own lawn, those four decide it.
I bought the occasional secondhand piece when I started. About five years in, I stopped. Unless you love working on mowers it's a waste of time. I can't think of one secondhand machine from those years that was worth keeping. If someone is selling because they're leaving the country or for health reasons it might be worth a look, but you're still buying a machine with no history, and that leads to trouble.
Avoid cheap gear from the big box stores. When it breaks it's expensive or slow to fix. A mate of mine owns a mower shop and has a contract to repair stock for a couple of big box stores. I've watched him cursing over those machines, bending parts to get them back into shape. He hates them, and for good reason. They're badly made with cheap parts.
The gear I recommend is for small commercial or domestic work. Bear in mind that a commercial machine can do in three days what a domestic one would do in a year, so anything on these pages will handle either job.
I build lawn care websites first, free. You see it live before you pay a cent.