You don't absolutely need to get a lawyer and an accountant to just start a little business. I would recommend going to the entrepreneur centre in the provincial building. They have a ton of free courses to take regarding GST, start up and that sort of thing.
You can also reference lots of info right on the CRA website.
Also, the federal building has (or used to) have a bunch of printed material on your responsibilities to the government.
As far as what sort of business to register as. If you're the only owner in your new business, then you have 2 choices.
Either a sole proprietor or a corporation.
There benefits/pros to a sole is its cheaper to file/start and there's less paperwork each year. Cons are that if you are sued or are liable for any damages or anything, then they can go after your personal assets, such as your home. Mind you, you can get some good insurance to cover your butt on a lot of things, you really just need to consider what type of work you're doing and the risks involved.
You pay the same tax your would as your personal taxes.
A corporations pros is you have limited liability (opposite of above, they can't go after your personal assets and your company could file bankruptcy, worst case scenario)
You pay less tax, but it's not going to be a crazy difference unless you're making a lot (my friend who's a chartered accountant said that if the limited liability isn't a factor then the second reason to become incorporated eventually is if your business grosses over $100,000 because the taxes will start making a difference.)
But just remember, you pay tax on profit, not revenue
Cons are that it costs about $1500 to become incorporated and there is extra paperwork involved each tax year.
If you have a limited budget, just keep any and all receipts you aren't sure about & when your year end comes, you can either hire a book keeper to do all your year end paperwork, etc then take it to whoever you want to do your taxes.
Bare in mind, the CRA lists expenses that can be written off, divided into categories. If you become familiar with the categories, when you get a receipt, write what it is so you don't forget or it's not a mystery Coke tax time. (Office supply, gas, tools to do your job, etc)
Finally, if you aren't selling a product, but only a service, you only have to charge GST, but you aren't required to collect GST until you gross $30,000 in revenue. Even if you only gross 25,000, it resets Jan 1. If you hit 30,000 mid-year, you just charge starting from there on (I can't remember if it's the start of the month you anticipate hitting or the following after)
If you do mostly services and only a small amount of selling products, you're allowed a certain amount without charging PST, but I'm not sure of the rules. Could easily be looked up on the CRA website.
Hopefully this answers some questions. PM me if you need help or have any more questions.