It depends on planet conditions and MNSF. You could have taverns making the most money on a planet (for example) but if more of them get built they'll make less and offices and hotels might start making more. There's no straightforward answer to this. If you're looking to buy an income facility, just ask for a record of its past income, or what you should expect its income to be, before buying.
For its size, hotels are some of the best producers earning roughly 50k at optimum stats. However other facilities can produce more (like casinos that generate ~80k but you can only have one per 4 cities as opposed to hotels where you can have 4 per city) but they are bigger and have lower numbers per city to get optimum income.