To second what Magooch said about a boat having a lot to do with how far you go in kayaking. I have sold sporting goods for decades and have often found that people seem to assume that their first mountain bike, roller blades, or whatever, should be small and cheap, as though beginers don't deserve good equipment. You can learn, and advance, in a sport better on good equipment than you can with "entry level" stuff. If you want to paddle on a lake great, but is that all you will ever want to do? Once you prove yourself on the lake you may well hear the call of the sea, or the call of whitewater. This should be a consideration.
Another factor that is often overlooked is who do you want to paddle with? If the people you hope to paddle with have kevlar sea kayaks that are 22" wide and you buy a short, heavy boat 26" wide it will be hard for you to keep up with them and tedious for them to slow down for you. Its not that one type of boat is better than another, just that the two paddling syles are not very compatible. Harleys can't ride with Vespas, although both are fun. Some kayakers are otters, they enjoy estuaries, swamps, protected backwaters and birdwatching. Some kayakers are orcas, they like the long crossings, open water, distant islands and ocean swells. Some of us do a little of both. One should consider buying a boat not just for the paddler that they are but also for the paddler they may become.