buying from seller who had option to buy?

New Jersey - I answered ad in paper 'condo for sale by owner" - very interested, but building owner/ condo association (?) tells me the seller who advertised, who's a lawyer himself, can't sell to me - he says the seller was renting the apartment for some years and recently decided to exercise his option to buy - this building owner/ condo association says that he is the one who owns the apartment that the "seller" has advertised, the seller can't sell to me because it's not assignable and he's just being sneaky and trying to "flip" the property. I'm very confused - I love this condo, but i'm not sure what would happen if i entered into contract with the seller who advertised. would i be getting into a legal mess or would it be ok to go ahead and buy? please help. (the seller of course never mentioned any of this to me on his own).

[HomeGuru]

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