Before you look around for web hosting, try to estimate service usage requirements based on typical use of your web application:
a. Bandwidth required
b. Number of average calls to database, per user, per time period
c. Size of database required to hold records
d. Processing requirements (CPU usage)
Based on this, you should choose from HIGH bandwidth & storage hosting plans with service-level guarantees. Don't just choose your service provider on price alone!
It also helps if the hosting service has a 30-day (minimum) money-back guarantee, so you can try running your web apps on their servers before you decide to stay with them.
You can check out typical budget web hosting plans here: http://www.iwebzhost.net/compare-hosting-plans.html
No matter which web hosting service you decide to go with, make sure you check out the Terms & Conditions sections before you apply.