Best thing to do is have lots of different people come and see him. Anyone who's interested and roughly OK (i.e can ride) should come and have a visit.
It gives you an idea of what you actually want and need and a better chance of finding it- I found that what I thought I wanted from a sharer wasn't actually what I needed. . Some people don't come across well over the phone but might be ideal so it's a shame to turn them down.
Letting someone have one shot on him isn't going to do him any harm and it's nice to let others enjoy the horses as much as you do (presumably you aren't one of these selfish, over-protective owners who doesn't let others so much as touch their horse
). And then you can see how you feel about them - when it's the right person you will know cos you'll be desperate that they say they like him and want to share
and conversly you'll know if they'e not as you'll feel relieved if they say he's not for them.
Set out some requirements and go from there. Think about the size and weight of rider you want (if he's a pony there will need to be a weight limit), the age (younger riders aren't always a bad thing.) and the ability - i.e the can walk/trot/canter/jump. And confidence is also important. Oh, and what days they can do/can they afford it. Other than that, don't be too fussy initially - make further decisions based on how they get on with the pony.
When you do have someone to see him, let them do everything with him and just get on with it themselves. Then at the end say you have a couple of others interested and you'll let them know at the end of the week. Then have them back again to make sure before making your mind up. It would then be worth having a months trial and keeping the names and numbers of anyone else who was interested, just in case
I've had loads of people come to see Brodie and eventually found the perfect people - kind and gentle but firm enough to work with him, and very reliable and hard-working. And they get on with all the other liveries and regually go out riding with them.
But there were loads of unsuitable people who sounded OK on the phone - a couple were far too heavy for him, a lot were far to quiet and nicey-nicey (he's a big bully) and some were just too novice. But one of the girls I now have sounded totally unsuitable and far too young (she's only 13) but is actually really good - she has restrictions of what she's allowed to do with him without an adult but is sensible and reliable.
As for will you get enough - yes - sharer are very sought after. Unless he's an idiot and needs a very specific rider/handler don't be too specific with the ad and you should get quite a few people interested - then you can narrow it down. Unless the price is high - but if you said something like 'pay of shoes' you should get a lot of interest.