Accommodation in Guatemala is cheap, and in most places you can find a bed for 20-30 quetzales ($3-4) a night. Many hostels charge per person rather than per room, so travelling in a couple won’t save you very much. A lot of them have a kitchen you can use though, so getting a group together to chip in for ingredients will allow you to prepare cheap, good meals.
The hostel scene gets annoying very quickly, arguably even more quickly than usual. It’s full of the sort of nauseating backpackers who think that going to a country with a name more than three syllables long makes them really fucking edgy. To avoid the most tedious of them, steer clear of those horrendous backpacker compounds that feature cutesy cabins around a mowed lawn with a bar/restaurant in the middle that organises quiz nights. That is, if you don’t want to be asked how long you’ve been travelling so many times you start fantasising about having your own brain sucked out through your eye sockets.
If you’re studying Spanish, many of the Spanish schools offer home stays with Guatemalan families. Prices vary, and it’s worth checking how much of what you pay actually goes to the family you’re staying with, as some schools are less honest than others.
In the rainforested mountains of the north there are a few cooperative Mayan fincas where you can go and stay for a few dollars a day, which’ll provide you with a bed and meals if you’re prepared to wield a machete. They’re not the most comfortable of places, but it’s worth it for the insight they offer into the lives and culture of the campesinos. They’re also quite an education in sustainable farming, though their methods of trash disposal might make you wince. Mosquitoes and some fucking little bastard insect they call jejenes will absolutely bite the shit out of you, even with repellent, so bring long socks and something with tight sleeves.
The cost of renting an apartment varies hugely around the country, depending on how far rich ex-pats have driven the prices up. But almost everywhere it’s possible to find something for $100 a month, as long as you’re not too picky about the exact location. On Lake Atitlan for instance, you can find places at that price at the uphill end of the villages, but if it is of crucial importance to you to be within spitting distance of the lake you could find yourself paying over five times that. Guatemala City is extremely cheap. Presumably because no one in their right mind would ever want to live there.