Have you looked into online accounts packages like...

http://www.xero.com

I use Free Agent myself (maybe more UK based)...

http://www.freeagent.com/?referrer=415n1kdu

Both support plugins and allow you to do all sorts of stuff.

I actually use Tave for all my online contracts, quotes, invoices and schedule. But this is aimed at photographers really...

https://www.tave.com

It is a workable solution for me, and all my clients love the fact everything is done online. Maybe it's worth a bit more research to see if one of the packages fits your needs.

Cheers

Cris