For your ticket sales idea, I believe Ticketmaster has exclusivity agreements with many venues that will block you out. I remember reading some time ago about a startup (this was long ago, can't remember the name) trying to upset Ticketmaster that ran into that problem.
Your Recurly idea will also probably be a headache regulation and compliance-wise.
Not to say they aren't great ideas, but probably not something you'd want to get in to without investor backing and a specialized team in mind to maximize your chances.
That might work depending on Paypal's TOS, but then again building your main revenue stream on someone else's API is asking for a headache too. Think Twitter or Facebook apps, but even more sensitive because it involves cash transactions.
Plus Paypal's reputation might make them think twice, depending on how they plan on implementing things.
I'd be very careful recommending PayPal for "recurring professional services billing" without doing a lot of research first...
PayPal is great if you're selling physical objects delivered within a day or two preferably with trackable delivery methods - thats PayPal's most favored transaction type since it minimizes their possible fraud losses about as far as you possibly can. The further away from that you move, the more likely you are to end up being another one of the many PayPal horror stories that are all too common. Things that can't be confirmed "shipped" by a disinterested 3rd party raise a flag. Things that can't be verified as having been delivered to a specific physical address raise a flag. Things that have long delivery lead-times raise a flag. I suspect recurring billing rasies a flag. I suspect high dollar amounts both raise a flag and act as a multiplier on other flags...
I strongly suspect this idea would end up with the PayPal account being stuck in the "can't make withdrawals for 180 days, but we'll continue taking your customers money so you're still on e hook for providing the goods/services right now" state, pretty much permanently...
Yeah, it is all suspicion - Paypal (necessarily) keep details of their fraud detection algorithm very opaque.
And I too, have many happy clients who've never had Paypal issues, even ones doing some of the things I listed above.
_BUT_, if you think Paypal in general are _not_ a source of _major_ headaches for some people, "I suspect" (there's my phrase again) that you've not been here long. Paypal account freezing has a long history of being discussed here (and elsewhere). I've been through that particular drama myself, in fact I've got one client who it happens to annually when he starts accepting pre-orders in Sept for a book that gets printed every December...
Your Recurly idea will also probably be a headache regulation and compliance-wise.
Not to say they aren't great ideas, but probably not something you'd want to get in to without investor backing and a specialized team in mind to maximize your chances.