Bear in mind that what I'm about to say applies in the UK. I have no idea whether (or by how much) the law elsewhere in the world differs. Also, I have only ever worked in a commercial insurance environment, so personal lines (household and motor insurance, etc. is NOT my forte). I'm offering my comments for what they're worth and not as "professional advice". Don't blame me if you get it wrong....
The general rule is that proposers / policyholders should declare all information that the underwriter might deem "material" to their views on risk acceptance, rating and / or other terms that they might require. As a homeowner's policy is amost always solely for non-commercial purposes, adding any form of equipment used for business purposes - whether used occasionally or full-time - carries the risk of the insurer declining a claim if the business use isn't declared to them and accepted by them.
Therefore, whether you're a photographer, plumber, electrician etc. you should be thinking about taking out a specific cover for your tools and equipment and ensuring that the insurer knows precisely the purposes for which they are used and the location / environments in which they are used.
The same comments apply in respect of your liability for injury and/or damage to third parties and/or their property - and, indeed, losses that third parties could suffer as a result of your professional negligence. Don't expect your homeowner policy insurer to pick up the tab for injuries/ damage sustained for your "business" activities.
Then there's your car insurance. Are you insured for "social, domestic and pleasure" purposes only? If so, how would you expect your insurers to react if you were involved in an accident on the way to / from a paid shoot? Might be worth checking, eh?
There has been a piece of legislation come into force recently called "The Consumer Insurance Act". This modifies the rules relating to the duty of disclosure as enshrined in Section 18 of the Marine Insurance Act of 1906 - which is the statute lawyers refer to when considering what is "material" as far as insurers are concerned. In essence, this piece of legislation places the responsibility on the insurer to ask for information they require to underwrite risks pesented by "Consumers" (you need to check whether you are a "Consumer" as defined under the Act). As a result, if the insurer doesn't ask, they may not be entitled to rely on "non-disclosure" to repudiate a claim.
However, the reason for non-disclosure can come into question and arguments can follow as to whether it was deliberate, reckless or unintentional.
This whole topic is a complicated issue and, to a large extent, it's understanding that if you earn a penny from your hobby, you could be construed as being a professional.
I can only recommend that you are completely open and honest with your insurers. Declare everything about what you do, where you do it and whether you earn a (partial) living from it.
Use an insurance broker. Give them all the information they need to get the best and most appropriate cover for you. Going "direct" to an insurer is okay if you really know what you're after and using internet price comparison sites is okay if you're looking for a general, one-size-fits-all solution. One obvious benefit of using the services of a broker is that so long as you've given them all the relevant details, if they screw up, you have a chance of taking action against them for their professional negligence - even if you insurers refuse your claim.
Finally, the fact that you paid £100 for a camera that would cost £1,000 to replace means you must insure it for £1,000 if you're on a "new for old" basis of cover. Insurance is no different to anything else - you get what you pay for and taking the cheapest option might prove an expensive folly in the long term.
