bring up to date ? .? built in the 1800 hundreds of normal brick with no preservation order on it .

My sister bought a house that needed most of the walls pulled down, new roof etc & they have nearly finished renovating it.

Sure, there has been lots of times where they have wanted the throw in the towel as sell it as a project but they stuck to it.

It is now really gorgeous & worth at least 3 times what they paid for it (before it is finished).

Renovate I say. You will get such a buzz from the finshed results of your own work & own design.

Good luck :-)

If you live in California, I could rebuild for you. That is, if you want to just get rid of the problem.

pull it down if its rotten

I would renovate & try to keep it looking has orindinal as possible.
Goodluck in what ever you decide to do.

having done the latter, I would say demolish and rebuild with a clean slate (unintended pun)

renovating is a lifetime task.

basically if the condition is that poor demolish and clear the site and build a new property using new foundations...
however there is a problem that demolishing a building might then mean you would be refused planning permission to rebuild.

get planning permission first for a completely new house from foundations up (plus that way you qualify for VAT relief making it 17.5% cheaper)

The question is too vague to answer. There are too many variables.