I would not sign on for any set time of treatment.. there might be fast results or no results, you might find that it is not helping at all and would like the option to stop going..
Any set or contract time frame is a bit suspicious to me..

And does this chiro only do adjustments?

The one I went to used many modalities like ultrasound, low level laser, NIMMO, IF stim, upper cervical adjusting...
I went for RSI/TOS and general wellness.

I suggest finding a multi skilled DC that does a mix of therapies and does not require any set time frame...