With 7 million, you should be set for life with a decent lifestyle.
To pay off the current house would cost me £50k, then spend half a million to buy a huge house to live in, along with all the gadgets, furniture, and solid wood you could need. After that spend 4x100k to buy four more houses.
That leaves £2 million to live off, plus the rental income of five properties, and a spare 100k to cover emergency repairs, and furnishings for the rental places.
If I won/earned/received £2 million I would probably need to keep working, unless investments did exceptionally well, but £3 would be sufficient for myself and partner.
I'd go insane with nothing to do, so I'd probably find myself working for a coffee shop or similar anyway, but the idea of the renting is to make sure I had a token-job, or function. (Hell with five properties and low fees I could probably become a management company..)
If you have a 7mm offer, and less than 1mm in net worth, take the deal (not, of course, before asking for more money).