Yeah the proprty will revert to the housing association one the lease expires. However, is your entering into a new lease the terms is usually 125 years plus. If you're taking over an old lease make sure you check the term remaining. 80 years is the magic number these days, if less than this it is advisable to ask for an extension. If you do enter into the lease and become the owner of the Leasehold this can be passed down through your will, again this can contiue until the lease expires but usually a renewal of the lease is possible subject to the housing associations' agreement. However, please note that you should speak to a legal adviser about this to avoid any doubt