Pulsar XP is not a microlight but it is LAA so cheap to maintain. I don't recommend the 582 powered one because you have a plane that needs 400 metres of smooth grass or tarmac yet has a microlight quality engine. That's why they are relatively cheap. Pulsars are compact inside and if you have a larger figure, say 12 stone +, taller than 5' 10" then you might not fit in.
Nothing wrong with buying a share but you must do research about the group and its history. There are lots of horror stories and con merchants around.
If you are buying outright check on hangarage first because that will determine a big chunk of your expenses. Certified aircraft will always cost you more but may be cheaper to buy because the annual maintenance can be staggering. Or not, if it has been well looked after. Ask around about maintenance organisations because these can vary greatly. And yes, there are horror stories here too.
My last two aircraft were previously owned by doctors and they were both looked after to a very high standard.
I've gone back to LAA aircraft after a spell with a certified plane. Our annuals were around £2000 which is at the low end for a 35 year old aeroplane but it was well maintained previously by a perfectionist and then a doctor!