Starting up in practice - what factors to consider?

I'm in the process of setting up a practice and have identified the following factors that need to be considered. Please can you take a look and see if there is anything obvious that I have missed? Also, in terms of accounting software, do I need to buy this at the outset, as my initial client base will mainly be sole traders and small start up companies? If so, can you recommend any good accounts production and tax returns software for a limited budget? Also, in terms of engagement letters, I know that ICAEW has some templates, but are these good to start with, or do you have recommendations as to where I can find/buy these templates?

The factors that I have identified, in no particular order, are as follows:

• Practising certificate
• Indemnity insurance
• Data protection registration
• Engagement letter
• Professional clearance letter
• Accounting and bookkeeping software
• Practice assurance (a whole topic in itself, I suspect)
• Impact of cloud computing and IXBRL
• Practice management software (is this necessary from the outset, or perhaps only needed when the client base expands?)
• Invoicing, billing and collections (although I plan to do monthly fees)
• Pricing
• Client monies
• New client checklist
• Anti-money laundering regulations
• Encryption of computer, back-ups etc
• Alternative (how do I go about arranging this?)

Thanks in advance for your help and advice.