When you are looking at a central heating boiler things are not always as clear cut as in this photo. However, the photo does illustrate a few of the things we look for when carrying out a survey:
the boiler is very old judging by its size and general appearance so it may have a limited useful life. It has not been used for some time and has warning tape all over it suggesting it has been condemned as unsafe by a gas engineer. And, it has an asbestos cement flue. Possibly, perfectly serviceable, but old, perhaps deteriorating where not visible and possibly unsafe as asbestos can be hazardous to health.
Unless recent satisfactory servicing documents are available, always get the boiler serviced at least every twelve months by an engineer on the gas safe register: www.gassaferegister.com. Never undertake work on asbestos materials before consulting a licensed asbestos contractor.