I bought my first home (1 bed flat) in 2009 on a shared ownership scheme. It was valued at 100k and I bought the minimum amount of 25%. I was single and had very good income, no debt so financials werent a problem.
I was going to buy more (max was 75%) but I was advised not too, the reason being that if I wanted to sell it at a later date, any potential new buyer would need to find a deposit based on the 75% which at the time, could be tricky, whereas finding a deposit on 25% could be far easier, I took this advise and I'm so glad I did!
I got a mortgage with Leeds building society for the 25% which worked out at £152 a month, I then had a ground rent of about £80 a month. Rent for the 75% came in at an additional 400/450 a month, however I was VERY lucky and negotiated a year free rent with the developer of the flat.
Just as I moved in, I met my now wife and 1 year, 1 week later we had sold my flat and moved into our house where we still are today, so I got very lucky that I never paid rent, so had a cheap place! I also made a 4K profit!
As part of the council rules, I had to let the developer try and find a buyer for my flat - at the time they have 3 months to find one and if they couldn't, I could go onto the open market myself. Fortunately they did via a special scheme they had going and the first people that viewed it, bought it. But again, they said if I had bought more initially, it would have in turn priced them out. Something to possibly consider. Good luck!