The base pay (taxable income) for an E-1 (lowest enlisted rank) is 1203.90 for the first four months of enlistment, then 1301.40 per month. Pay goes up with rank and time in service. This does not include housing, uniform, and meal allowances (non-taxable income). These typically vary depending on your location, job, and housing status.
A good website to check for the ins and outs of military service is usmilitary[dot]about[dot]com.