First of all do a survey to find out the problems with your property. Check the roof, walls and the floor. Basics like heating, plumbing, electricity also needs attention. If you need professional services call timber, roofers and dam specialists.
Legal documents and agreements related to property should always be clear. Minute details related to property lettings may be a real headache, but it needs to be carried out.
Check what are the existing problems? These may include the structure of the house, central heating, plumbing and electrics. You may discover various problems while renovating your house. For any work you do think on a long-term basis.