Paying off mortgage

When we have paid our mortgage off, would I be correct in my understanding that we can only live in the property as long as we don't sign another lease again? And that the disadvantage of not signing another lease is that there will no longer be a 'guaranteed' rent? Also that we are not required to sign another lease as long as we give the relevant notice at the required time? Are standard estate agents (who will only pay rent where tenants are installed) likely to take on a leaseback property? If not, could we have relatives move in and live there and pay rent once the mortgage is paid off? Therefore avoiding a reduced rent from a leaseback company? Presumably there would still be maintenance costs to factor in. If the expenditure costs (taxes foncieres, accountants fees, maintenance fees) remain in line with the rent received, even when we have paid off our mortgage, there will be no money to be made from the rent received, as it will just about cover our costs. What then would be the advantage of buying a leaseback? I ask because I read that a leaseback was sold recently and I am wondering why anybody would buy a leaseback...