I'm looking to set up a small chemistry lab in my garage for doing demos. I think it would be good for a freshman student I'm mentoring and also as a hobby. Does anyone know where I can buy apparatus (like flasks, pipettes, heaters) and chemicals?
If you live close to a research university, I would recommend you to look up if they have a surplus store. Often times when professors retire a lot of the lab supplies get sent to surplus, where they are sold very cheap. You can also build equipment out of basic stuff you can find at any thrift shop (pressure cookers, blenders, etc).
As for chemicals, it really depends on what you are interested in doing. Metals are all around you. You can take some pennies, dilute hydrogen peroxide, any carboxylic acid (vinegar, citric acid, amino acid supplements, etc.), and stick the mixture into a microwave for a few seconds. The copper will form complexes with the carboxylic acid you add. Different acids will give you different colors. Leave them standing for a bit and you will get crystals.
If you get to know the plants around you, you will have access to a huge array of naturally occurring small molecules and enzymes. Some palm trees have a high concentration peroxidases, onions and garlic undergo some pretty cool chemistry which results in the formation of pigments (blue, green, pink), there's pH indicators, capsaicin, etc.
Buying pure chemicals for organic synthesis is usually tricky, and for many of them you need to be affiliated with a research institute.
There are several YouTube channels with chemistry experiments which mentions where they obtained the chemicals. I recommend 'NurdRage'.