There is no right or wrong way of going about dealing software for your first client. If you are happy to promote the benefits and costs of a subscription package like Xero from the outset then go for it as it makes it really easy to pass on the cost to the client.
It may be worth you trying some of the other types of software around that are not expensive when you first start, just to get a feel for what is out there. I started with VT+ as it was a 60 day demo, cheap for a bookkeeper starting out and is really simple to use and I used this for about a year alongside a copy of Sage that an accountant I work with provided. (make friends with an accountant they may be able to help you with this!!) Solar is also another company that offers a good, low cost option when starting out and a good length demo period Moneysoft money manager is another alternative that's worth trying.
I found by having a background knowledge of different product it helped when talking to clients about software, not all of them like the idea of the cloud, some what to get involved, some want nothing to do with the paperwork and couldn't care less what you use as long as it's done and they don't get fined!!!
I hope that makes sense???