First off, you need more than one crab. In the wild, land hermit crabs live in large colonies and they get stressed when they are alone. For 2-3 crabs, you will need minimum a 10 gallon glass tank. If you get 4 or more, you will need a 20g or larger.
As far as heat goes, you need to keep your tank between 75-80 deg F at all times. This means having the heat on 24/7. It's acceptable to turn off the heat lamp during the day as long as your house does not sip below ~71 deg F. These crabs come from near the equator! They are active at night and need a warm environment. To heat my 55 gallon tank, I use a 150 watt bulb and ceramic hood. You probably want to go with a lower wattage for a smaller tank, but both of these items can be found at this online store for pretty cheap! http://www.petdiscounters.com/ Their shipping is also very cheap.
For water bowls, you need something that is deep enough for your largest crab to submerge in and you need to have a way for your smallest to escape. I find that plastic or glass tupperware is the best way to go with rocks propped up in them so they can get out. Also, they need both fresh AND salt water. But you need to dechlorinate your tap water using drops meant for aquariums. You also need special ocean salt used for aquariums. Table salt is toxic to crabs.
The supplies you will need and the best place to buy is as follows:
10g tank or larger: buy locally
Playsand or Eco-Earth bedding (twice the height of your largest crab, and moist enough for them to tunnel): http://www.petdiscounters.com/ for Eco-Earth or walmart for playsand
Extra shells (3 per crab): http://www.hermitcrabpatch.com/
Food: http://www.hermitcrabpatch.com/ and feed fresh foods from this list: http://hermitcrabassociation.com/phpBB/viewtopic.php?t=64004
Water and food dishes: Buy locally
Dechlorinator and Ocean salt: http://www.petdiscounters.com/ or locally in aquarium section
Decor: http://www.petdiscounters.com/ or locally
Heat lamp/bulbs: http://www.petdiscounters.com/ or locally
Hermit crabs can live for up to 30 years, but sadly, the information that is written on them is horrible. Fortunately, there is a community of hermit crab experts that I think you should get involved with. The website is http://hermitcrabassociation.com/phpBB/ They are all very helpful and supportive. They helped me so much in the beginning. All my crabs would be dead by now if it wasn't for them. I really reccomend giving the site a visit. Poke around a little, and join if you want to! :) Hermit crabs aren't for everybody because they need a lot of very specific care, but they are neat little creatures.