Well good luck with whatever you decide,
It wouldn be an option to take the place on a hire purchase scheme?
In that case any money spent on repairs or rectifications would be seen as an investment in an asset. All money put toward the place would in fact be working in your advantage as you would be increasing the value of the unit.

Alternatively u may be best served to agree a long term rental period, lets take for instance twenty years. There is no way in hell you want to invest money into a place where u will be leaving within five-ten years. Additionally you may want to investigate ur legal rights to almost operate as a sub-contractor. i.e Renting thge place for twenty years, obviously meeting all payments, living there for say, five and then in turn renting it for a profit to a third party?

Contemplate the potential pros n cons, think of a plan that will benefit the future while satisfying ur current needs.