Pros: Cheap as dirt. Annnnddd that's it 😉
Cons: Cheap build quality (you get what you pay for), misaligned screw holes, pointed edges that more expensive cases don't have, poor looks (have you ever seen a bada** case for $25? Me neither 😛), harder to install drives, and especially cheap fans. Terrible airflow. I have bought a case that came with only one exhast fan... that was DOA!
If I were you, dip a bit more moolah into a case. The upgradability will save you time, money, plus you won't regret it.
My best guess would be dipping at least $60 into a computer case. Seeing as you may only want to dip very little, I would like to give you some advice: research! A $25 dollar case would last you maybe a couple of years IF AT THAT...