Regarding the accommodation in Olomouc, please, check the the booking.com

Here are some recommendations:

The cheapest option in the city centre: hostel Ubytovna Marie

Cheap hotels close to the city centre: Hotel Gól Garni, Cosy Corner Hostel, Hotelový dům, Hotel Palác, Penzion Moravia, Penzion Bellis, Apartmán Dukelská 8

Hotels in the historic city centre: Hotel Penzion Na hradě, Penzion Arigone, Pension U Jakuba, Hotel Trinity