I can't say that it would have been "obvious" had you not mentioned it. It's a pity because, as new startups (both online and offline) are often told, you cannot do it on the cheap and expect results.
Firstly, Wordpress: I have seen some (perhaps less than optimal) e-commerce websites that were built on Wordpress at a pinch by people who knew what they were doing, but I cannot recommend it. If you want a CMS for e-com - and you really do - use Drupal or MODx or opt for some good e-com software auch as Actinic.
You really need to work with a professional. I am bound to write that, but it's my honest opinion. I hope that you are not underestimating the complexity of this topic.
Hosting: you will need PHP5, MySQL, fairly generous bandwidth allowances, and no minimum package contract in case you need to upgrade. Heart Internet's mid-range Home Professional will suit you.
Payment handling: figure out what you want to use from the many options, each of which have pros and cons. Too much to go into here.
High-res pics: that will eat bandwidth and annoy visitors, so go easy on that idea.
Legal: e-com means knowing the relevant laws and abiding by them. You need to know the SSGCR, DSR, etc. (all the common retail/consumer law regulations) and the site must meet minimum accessibility standards (because it is providing a product or service and must not deny disabled access to that).
Search engine optimisation/marketing and offline marketing: Cannot under state the importance of that. You will need to market at least as hard and as smart as your competitors already do.
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