Hi Theeka,
You can start a routine on any beat, there are no competition rules that would prevent that, and obviously none in social dance. However, if you do social dance, start whatever you expect your partner to start, it could depend what the studio teaches. In CC, usually on 1 the man closes the LF to the RF (prep.step), so he can start a basic figure with a back check on the RF on 2.
This is pretty safe, in social dance, as there is no chance to step on the lady's foot (at least not on the beginning) which is the principal law of social dancing. So if your studio has a definite tradition, follow that, otherwise you are safe with this suggestion.
With more advanced followers this is not a problem as they automatically follow, regardless on which beat you start.
You may notice that many Latin dancers first dance step (as a preparation step) is on 4 in International Rumba, not on 2. In Rhythm Mambo there is usually a prep-step on 1. Most International Standard dances use the last step of the prior measure as prep-step, before dancing the first figure.
The prep-step, in my mind, serves two functions: 1. Puts the body in motion; 2: helps with counting the beats.
Hope this helps. Good dancing.
