How to make sure technical staff won’t hold site hostage
First I want to address the point that any contractor, or employee you have working for you, you should trust. It’s unprofessional to hold a site hostage when you already paid them to make it for you. If you don’t trust someone don’t work with them period. That being said, development is a lot of work, and non-technical people often underestimate how much work simple changes can be. If a technical person says something will cost a lot of money, you should trust them enough that they aren't trying to rip you off. Often people with technical backgrounds have a tough time expressing to other people what needs to be done, and why certain things will be more expensive than others. Try to build a mutual understanding.
You should ask your staff questions about why something will cost so much and what could make it cheaper? Try to get a better understanding of what needs to be done. You can also ask this person how they can give you more access and oversight into what they are doing. Express your concern by asking them something non acuistory like: “What if you get sick. What should I do?”. Any consultant should be willing to walk you though how you can easily transfer the project to someone else.
If you are in the position where you don’t trust some one you have hired here is what I suggest you do:
Get a git hub account
What is github?
Github is a version control system. Think of it like a word document that keeps track of all the changes you make but it’s for code. Programmers use this so that they can easily see the changes they made in the code and quickly go back to older versions if there are bugs. Any programmer should be saving their code on a github (or github like).
Use Git hub to track when the code is changed and keep control of it.
If you have a git hub account, you have control over where your developers upload their code. This way you always have access to what they have built and can give it to their replacement. Just make sure you get an account with private repositories because you want to make sure that only the people you authorize will have access to the code. If you are unsure you can always ask the developer you are working with to set this up for you. The developer and you should have separate accounts and you should be the account owner, so you can block access to whomever you want.
Make sure they comment their code
Good programmers create code that is readable to other programmers. Part of that involves comments and thinking about code in simple terms. As someone without a technical background it can be hard to tell if the code someone is producing is good. Good programmers will do two things: make their code readable to other developers and use existing code rather then build it themselves. In the github account you can see if they added comments to the code as an easy test to see if they care about making their code readable.
Overall I don’t think you should be afraid of technical service providers taking advantage of you. Most won’t, but they maybe a bit awkward and inarticulate. I’m sure if you just have an honest conversation with them they can help find a suitable solution where you both feel comfortable.