Well, come April 15th surely you need to complete all sorts of W2's, 1099, 1045 and whatever, the states have similar forms, if your's don't agree with what the other folks that provide you income or charge you money do on their forms, then sooner or later expect a call/audit. cities at least around here expect a business tax from you if you are in any way in doing business in their jurisdiction, that is both where you are and where they are.
Abstract what is needed for voip to work, Three things that must ALWAYS work . Inbound Calls from the PSTN, Outbound calls to the PSTN, so derivitivly and most important an internet connection in the absence of a PSTN solution, PRI's BRI's or even just a phone line
So I suggest most importantly BGP in front of a multi-homed SIP proxy in front of a multi-homed internet. Then redundant outbound routes for failures of VSP's or call routing, and absolutely if using Asterisk an immediate and effective failover HA solution , I would go with KVM, perhaps ProxMox, you are left with indound DID's , either go on the exchange and buy you own (but you would need 100k's or more minutes a month to justify that) or make sure that your VSP has an effective failover policy and you yourself have an equally effective failback policy
Three things that aren't 5x9's Asterisk ( never will be ;-) ), your VSP (Don't know of one yet), and your ISP (that is related to cost
)
Generally all the above is moot as anybody who buiys cheap shit expects it to break quite often, it's just that you really don't have to break as much as most folks do.
Good Luck