where are you ?
The going rate for buying a free hold is ten times the ground rent
I pay £50 a y ground rent - so it would be £500
obviously different in London and you also have to look at how long the lease has left to run
I am in Manchester and with rates such as I have described the usual advice is that it is never worth buying the freehold
Your circumstances may be commpletely different
for a start you would be buying a 'flying freehold'
as or adding it onto your mortgage ask your morrgage lender -
it will depend on how much equity there is left in the property