Spot clean wet areas every few days but the main cage with deep substrate may only need a full clean every 6 weeks or so. This would apply for a really big cage with nice deep litter so they can burrow. Take a look at the housing board and maybe ask members there - it is harder to get decent sized cages in the USA however you should manage it for dwarf hammies. Making a bin cage is quite easy and there are lots of online tutorials on that. Scatter feed them (no bowls) and don't let them have small enclosed areas they can fight over as territory. Give them as deep litter as you can so they can burrow away from each other and they really need two of everything if you want to keep them together. One can also bully another and hog the food - is one smaller?
http://www.hamstercentral.com/community/housing/