Don't have much cash but want to record. Here is the essentials you will need to get started.
Grab a versatile mic like an sm58 and find a decent audio interface depending on how many channels you need.
Can't afford a DAW. Check out audacity of if you have a mac use Garage Band. Studio Monitors don't have to be a months rent. 
If you can't afford monitors off the bat check out a decent pair of over the ear headphones not ear buds.

1. A microphone
2. An audio interface
3. Digital Audio Workstation (DAW) software
4. A digital keyboard
5. Studio monitors
6. Headphones
7. Cables