Don't assume that just because a company sells and installs solar panels means they are good and trustworthy people. Shop around. Get a minimum of three quotes. Read all contracts. Check backgrounds of potential contractors. Deal with this like any other home-improvement project that you would otherwise do.
If you're thinking about installing solar panels to generate your own electricity, make sure that the roof you'll be installing them on gets plenty of good sunlight. Good sunlight occurs between 9am and 3pm. You'll generate the most electricity if your roof receives full, exposed sunlight between those hours every day.
Overview of the power characteristic of solar panels, common MPPT algorithms, and a simple low power reference design to maximize battery charging current.
When you can't afford a full system, instead start with a solar water heating system. Water heaters make up a large portion of the energy that a home consumes during the year. Your costs are going to be lower upon installation of your solar water heating system.
Carefully consider the types of solar panels you plan on having installed. Long ago, if you didn't have enough roof space, you'd need very expensive high efficiency mono-crystalline panels. There are now more advanced polycrystalline panels and even thin film panels. If you've got enough roof space, you might wish to look at the size of the panels in relation to their output capacity to avoid having insufficient panels that you need more of later.