Hi Mares,
Those prices look a little rich given what the local area is like. The locality is very mixed. Further south you have smart areas such as Highbury fields and Islington, but just 10 minutes walk north of the stadium is the Seven Sisters Road - a fairly grotty part of North London (also close is the Finsbury Park mosque where Abu Hamza used to preach). A 4-bed renovated victorian house in that area would set you back about £550/£600k vs. £295k for a one-bed appartment in the development. Also, a 6% yield does not look that great when you can earn 4.5% with an internet bank account in the UK. For the same cash, there is probably (relatively) better value available in the surrounding area.
Having said that the area will certainly improve now the stadium is moving as the hoards of fans and associated rubbish/noice/drunkeness move 1/2 a mile further away.