There are many advantages to making your own baby food. First and foremost you know exactly what your baby is eating. It is much cheaper than food in jars, even on sale. And it tastes so much better. I have no idea why jarred carrots should taste different to mine, but they do.
The disadvantages include the fact that it takes a bit of your time and your baby just might reject the jar of food you try to feed him or her when you are out and about. (My son had a few jarred foods I could rely on for him to gobble down whilst out).
If you cook already, it really isn't that much of a problem to make extra for the baby. To begin with babies start with rice cereal or something similar. But shortly after this you can start single vegetable purees. My doctor told me to start with vegetables. She told me that babies always like fruit, but if you give them apple first, they may prefer the sweetness and reject peas. Most people agree: start with carrots.
You need to gather some equipment:
Ice cube trays
plastic freezer bags
or plastic food containers
mini food processor
I find it easier to either fit the cooking into my nightly meal prep or find a bit of time each week to dedicate to the task.
When you have a bunch of carrots on hand, steam or boil them until tender. Pop them in the mini food processor. (I have an attachment for my stick blender). Puree using a bit of the cooking liquid if need be. In a few months you will be blending this leaving a few chunks. Put the puree in the ice cube tray. Let this cool and cover in plastic wrap. Freeze until firm. Pop the carrot cubes out and put them in a plastic bag or box with lid. And back into the freezer.
Repeat this process with spinach, butternut squash, sweet potato, peas, apple, pear, peaches, green beans, and parsnips. Not all at once! Just as and when you can put a pot on the stove.
I have a small drawer in the freezer where I have my baby food cubes. When I want to rustle up a baby dinner I grab two carrot cubes and one spinach. Or one apple, one green bean, and one courgette. Or whatever appeals.
Some baby books recommend trying one food at a time for three days. And some baby books say to never feed a baby the same thing within three days. You can read up on all of that and make your decisions. I know there are a lot of allergies out there. I even know of a child who is allergic to onions and leeks. But most babies are not allergic to peas and carrots. (Fruit allergies are the next big thing I hear).
As your baby grows, you need to make sure your foods are lumpier and before you know it you will simply be mashing what you are cooking for your dinner----before you add salt to the recipe.
This is just a taster. If making your own really appeals then you can get some good books out there. Annabel Karmel's books will become your bibles. But there are loads of baby food books out there with great ideas for weaning, toddler meals, and family meals to appeal to adults too.