Here's a cheap option for a B&B in Bad Aibling. It is a very small one, the owner has only 3 rooms: 2 double occupancy and a single occupancy room. The two doubles have a private bathroom within the room, the single has a private bathroom outside the room. Here's a tip ask for the double occupancy room on the 3rd floor as it has the best view (all have balcony access), but it also comes with a little reading room across the hallway. For a very small fee (I think it's about 1.- EUR) you can use the guest kitchen. Breakfast is included, but it is a European breakfast - so don't expect bacon or pancakes, it's more breadrolls, jelly and sliced meats. The owner keeps beautiful flower gardens around the house and you can see the alps from the balcony.
The center of Bad Aibling is only a short walk through a beautiful birch alley away (15 min walk) or you take the 0.50 EUR bus.
Enjoy! If you have any questions feel free to contact me:
PS: The owner doesn't speak English very well, but you can make reservations online if you google their name.