I also often check the korean websites - hotel365.co.kr and yanolja.com as they have a lot of motels listed along with photos so you can get a few ideas and names ahead of times. They are in Korean but will translate with google. They also list prices but it can be confusing as they will list the day time rate of 3 hours first. So disregard the lowest range of prices and go by the second set which translates as accommodation and is for the standard room to suite rates overnight . If you get google to translate the day time rates it translates as terribly disapointed- not sure thats an ideal translation.

Some motels are designated "Goodstay" by the tourist authority and have to meet a standard. They are more family hotels and don't usually function as love motels.

Hanoks - traditional Korean style buildings are nice place to stay. They are usually small. Rooms have sleeping mats not beds so its going to be hard but the floors are usually heated. This last trip we stayed in one at Gyeongju called Cochari Hanok but is listed on some booking sites as Floral Space Guesthouse. Its a lovely place with a beautiful garden courtyard very near to the tomb mounds and other sites. They provide a simple breakfast in the common room. They also have an excellent coffee shop at the front which is open in the day Cost was around 60k but is probably dearer on booking sites. We ended up there unexpectedly as we were travelling on but an urgent meeting the next day meant we needed to head in another direction. It was sorted for us by a friend who knew the owner.

There are also homestays and airbnb is growing.