Solid construction year and I find it charming. I'm into old buildings anyway. I would renovate it if your parents need something anyway. You can also rent it out well after your parents because it is detached and has a pleasant size. For cost estimation... hard to say. Our house was also very run down inside, we have so far invested about 60,000 in the renovation (ceilings, floors, walls, 2 WCs, 1 bathroom, roof insulation, interior doors, sanitary, electrical, radiators (gas boiler was fine), windows, roof windows; still missing a new front door, 3 windows, exterior plaster of the basement, new basement door, 2 interior doors).