How about a Yamaha Fazer?
You won’t get one of those for £500.
Or much else for that matter. Used motorbikes hold their value amazingly well. I’ve had a few around the £500 mark and without exception they’ve all had major issues. A £500 bike can easily need £200 tyres and a £400 exhaust within 1000 miles of buying it
There’s also a LOT more to it than buying a bike when it comes to economy:
How long do it’s tyres last? How much are a pair of tyres?
How often does it need servicing? – Lots of bike have 4000 mile service intervals and need regular valve adjustment. Can you di it yourself?
How long does a chain and sprockets last? I had a CB500 and it was tough to get over 10,000 miles out of a set at £90 a shot. Parallel twins and singles are known to get through chains. It’s not power, that kills them, it’s engine configuration. The Speed Triple I had after the CB500 was still on it’s OE chain at 33,000 miles in which time the CB500 with half the power had done 3 sets
Fuel Consumption: Yes, bikes can be good on fuel. But if you pick wisely you’ll save a packet
Insurance – With no no claims it’s gonna cost you. I’ve just insured a 700cc bike fully comp, unlimited milage, 2 riders, for commuting for £89. But I’ve got 12+ years no clams, I’m 43, and have been riding continuously for 15+ years. Starting from scratch won’t be cheap.
Then there’s clothing, somewhere to keep it, chain lube, adjusting the chain… etc 🙂
Not trying to put you off, just pointing out stuff that you need to be aware of!