If you are using a freelancer or studio for any web solution you need to make sure you have a contract in place (and understand what it's saying) before handing over money or allowing them to start work.
You need to make sure they set clear milestones, have discussed your needs clearly and understand them. That the payment points through the project are reasonable (most require a % upfront and then periodic payments when specific milestones are reached and you confirm that you are satisfied up to that point).
Be wary of those who ask for what seem to be slightly unsettling payment terms or payment terms that seem too good to be true (i.e. no payments until completion; most companies wont do that as the client can play games; or most/everything upfront).
Also, look at what your paying, the timescales and what's being promised. If it sounds too good to be true, to be blunt; it is.
In other words; clear agreements that protect both parties are indicative of what kind of company you are working with; if an agreement seems fair both ways; you are probably talking to a fair and reasonable company.
I wouldn't agree with avoiding freelancers and studios because you can be held to ransom either; I've never done that and don't know anyone who does.
Also, with the way we operate and most providers I know operate, you aren't tied in as you get the full sources in your hand on sign-off. Working with the provider long term is something thats built on a sustainable, beneficial relationship not a "lock in" and if a provider needs to lock you in, it probably means their relationships are not organically sustainable or mutually beneficial.
Another thing to look out for; I wouldn't use any company who would not hand me everything at the end of it.
Being held to random is one problem, but what if they go bust down the line or for whatever reason cannot assist you with something you need doing in the future. You are stuck.
Hope all that helps if you do choose to get a freelancer or studio to create your site for you.
