It all depends on what you consider “decent”. If you’re coming from a major city in the US, you might find Taipei to be somewhat interesting in that you can find places in Taipei that are quite cheap located not too far from places that are quite expensive.
You could rent a furnished studio (basically a small room) of 250 to 500 sq. ft. in Taipei for under $20,000 NT (~$700 USD). These types of units will likely be in an old(er) building of typically 1-5 stories. Some of these won’t have elevators, most won’t have front desk staff (to accept packages, etc.) and you’ll probably have to deal with your own trash.
You could rent a slightly larger place with a bedroom and a kitchen for anywhere from $20,000 to $45,000 NT ($700-$1,500 USD). Depending on your location, in this price range you might still be in an old building, or you could be in a newer building. In a place like Da’an, for instance, you’ll probably be in an older building. In a place like Neihu or Nangang, towards the higher end of this range you could be in a newer building with some amenities, such as on-site staff to accept packages, etc., as well as trash removal.
Finally, you could easily spend upwards of $50,000 NT (> ~$1,800 USD) on a larger and/or more upscale apartment in a new(er) building. These will typically have on-site staff to accept packages, etc., trash service, and they might have a gym and lounge. Some will even have pools.
So, put simply, location and size matters a lot, as does the nature of the building (old, unstaffed versus new “luxury” build).
Once you figure out the locations you like the most, you can use the map search on 591 (地圖找屋-591) to get an idea of what types of apartments are available in those areas and what they generally go for.