I just start SilverStripe today and after experimenting for a while, I started wondering whether it is possible to build simple invoice that clients could just access and pay via Paypal - nothing fancy but basic invoice. It would help to save money on freshbooks especially when I am just starting out.
Please kindly share the experience and how you do it. thank you in advance!
Ya I personally wouldn't suggest getting SilverStripe to do it. Not that it couldn't, but why reinvent the wheel when there are other options out there?
I personally use http://www.workingpoint.com Their free plan pretty much would do everything you need for a starting out freelancer. It's only been out a few months, so it is missing some features like recurring invoices, but I love it and those features will come. It does more than just invoice as it's really a whole accounting service with a super simple and intuitive UI.
That siwapp program looks interesting though. Will probably test it out for the fun of it. Had never heard of it before.
Membership websites are certainly possible. I am assuming you mean more then just register and blog content, for example some paid membership service. Either way its yes you can - We are currently building a rather large site which requires member payments now.
If you are looking for some code to start have a look at the registration module which enables users to register to the site. If you need payments have a look at installing the payments module with it. Note you will need to write quite a bit of custom code.