In Vien Viang, you can get a single room with fan, and private bathroom for 30,000 Kip, with wifi. I have found two places that do this so far, so worth a look around. Most places will have singles for 40,000 Kip, or you can save a lot more money in a dorm.
Eating can be cheap, you can get a good noodle soup, Pat Thai, sandwich, or pancake for 10,000 Kip. You can also get a big beer lao for 10,000 kip, or at times of the night, buckets go for 10,000 Kip as well (The Bucket bar on the island, before 10pm). Or you can get a bottle of Laos Whiskey for 10,000 Kip as well. Big bottles of water for for 5,000 Kip.
You can easily find places to do your laundry for 5,000 Kip a kg, to pick up the next day. Be careful though, the first lady I went to was using a dodgy weight machine, that doubles the number of kilos my clothes were.