I've done shared ownership. I found it a mixed bag. It worked for us, but I think from what I know and our experience we are probably the exception rather than the rule. For most people I think its only really viable if you NEVER have a chance of anything else and you intend to stay in an area permenantly (having something that ties you to an area in addition to work, like a family connection is a probably key consideration) and are unlikely to want to step up the property ladder in the future. If you could save a bit longer and then buy, I would tend to lean that way tbh, knowing the pitfalls.
We eventually bought the rest of the property but we had various issues with dealing with solictors when we bought initially, when we scaled up and when we sold on. Make sure you get a solictitor with experience in shared ownership if you do decide proceed. We also had a restricted number of mortages we could apply for. Not all mortages are available for shared ownership. And this of course means you get stiffed for a higher interest rate.
We did ok with shared ownership. It worked for us, but i do think it only really works for most people if the housing market is rising - you can get completely screwed and trapped if the market stagnants or drops. If you end up going into negativity equitity or financial trouble you can't sell, but you also can't rent the property out. That might limit your options for moving elsewhere for work. It only worked for us because although the market just stalled (we bought in 2007) DH's salary increased significantly and we over paid on the mortgage. If it hadn't we'd have ended up in a situation which others in the estate have found difficult - our scheme had a rent attached to the portion of the house we didn't own. This increased annually in line with inflation. We bought our way out of it, but a couple of our neighbours ended up in a situation where they were paying mortgage + rent for the property which was MORE than we were paying in mortgage for the entire property even though the property was worth the same. One of them ended up having switch to an interest only mortgage to keep the house - she couldn't afford anywhere else locally to buy.
So think about what your long term goal on home ownership is about - is it about a secure roof in an area you can't afford, a stepping stone to full ownership avoiding renting etc? Keep focused on this. And I would encourage prioritising over paying on the mortgage on shared ownership in a way I wouldn't for a normal ownership because of the trap of shared ownership.
We also know that some of the shared ownership properties on the estate had a problem with being sold on - and I've heard of the problem elsewhere. The issue is because you don't own the property outright you are restricted on the sale price when you come to sell. It effectively removes your ability to drop the price slightly to accept a lower offer than the asking price. You also can't easily reduce the price if the house isn't selling. The inital valuation therefore is key, and has to be agreed with the housing association who own the rest of the property. The worst case I've heard of is a friend of a friend who was in a situation where the housing association wouldn't reduce the price for 4 years which meant they were unable to move.
Our estate was in a really nice and desirable area and mostly larger detached properties. Our section of the estate was smaller houses and was great, but there was another part of the estate which had shared housing and social housing which did seem to have an antisocial problem.
As a rule, the shared ownership homes on the estate, despite being cheaper than anything else in the area, tended to take a long time to sell. This was despite a clause in our property that meant that if there were no interested parties for shared ownership, the entire property could be sold at 100% value too. Like you, people are more hestitant about buying shared ownership. That limits your potential pool of buyers. If you haven't got a clause to allow you to sell to a buyer who wants 100% of the property, thats another thing which might trap you to the property.
The things to look hard at are management fees, rental fees and anything which might limit how you can sell in the future. You don't realise how important and significant tiny details can be in this. We are very savvy and sharp buyers and had a solitictor who was very good at shared ownership. Others who bought on our estate had shocks later down the line with things they didn't realise in the terms and conditions.
For me, from what you've said my concern would be with the homeless tenants and whether you would get an anti-social problem developing (which could impact on the saleability of the house). Its a huge wildcard which could add to the danger of the trap of shared ownership. It would be a very serious red flag to me tbh.
I think Shared Ownership definitely has its place. It worked for us, and I think its good for a lot of other people but its not without significantly more risk than normal ownership.