First, you don't need expensive lessons to learn art. Sometimes those are useful, but they are not required. Anyone can pick up a pencil or a paintbrush and start making art. People have been arting since Neanderthal toddlers dragged their fingers through the mud on cave walls.
Second, you don't need expensive materials to learn art. Sure it's nice to have high-quality media, but there are drawbacks to that too. Fancy things can be so finicky that novices can't handle them well. The cheapest media may have limitations of their own, but there are still things you can learn from them. If you can afford it, student media typically offer a good balance between the extremes.
Here are some fast, cheap options for exploring art:
Sketching is a great place to start. You can do it with any pencil, pen, or paper. If you want to go with formal art supplies, this is one of the cheapest options in terms of getting decent stuff. There's a range from basic to fancy sets. You can get a very nice beginning set for less than $10 and the big sets fall between $50-100. It is usually cheaper overall to buy a set, but with very limited funds you can buy things one at a time.
Watercolor is among the cheapest options for paint. Even the kind you can get for a buck at a dollar store will be adequate for basic exercises such as shading and flow control, or experimenting with additives like salt. You won't get the full effect but you can practice.
Buy 1-3 colors of art student grade paints at an art store, and practice with those. They'll do almost all the things that professional grade paints well, at a more affordable price. This works with watercolors, oil, and acrylics. You can learn a lot about the primary colors this way. Black and white are also good choices.
The first time you buy a paint set, get one with a minimum of colors, like 6-12. You do not need 30+ when you are starting out. You need to study the medium and learn how to blend your own colors.
Get a small tablet of paper or set of canvases to start. You don't need a big space until you're painting complex topics. A small one is plenty for practice exercises and painting small, single objects. Bigger surfaces cost a lot more. For charcoals, pen and ink, or other relatively dry media you can use regular notebook paper; it's fine for practice even though it's not very durable. For watercolor, you really need the special paper. For oils and acrylics, canvas board is a cheap alternative to stretched canvas.
If you want to push yourself, take a mini-kit to a park and do some plein air painting. The point is not to duplicate the scenery accurately. The point is to see how much you can do with 2-3 colors and a small pad. Plus it's great practice for later: you do not want to lug 60 pounds of equipment through the woods. A good plein air kit is small and light. When you're familiar with a small palette and can afford more materials, then you can expand it.
To learn faster, study anatomy. It's fascinating, it's useful, and it will automatically improve the anatomical aspects of your art as you learn more about how human and animal bodies go together.
Gray's Anatomy is the go-to reference for artists, especially the various levels of coloring book. Keep that in mind for later budgeting. (You might want to make a list of art supplies to buy; you can't stock a whole studio at once.)
But you don't need to spend money on it. There are loads of anatomy websites, coloring pages, worksheets, etc. online for free. Just search until you find ones you like.
Once you've got the hang of using anatomy to inform art of bodies with the meat on, step up your game and try imagining meat onto skeletons. Forensic art is an actual profession now, but it started as an art exercise. Remember the still life skulls? That's why you want one. You can find lots of references for extinct animal skeletons online, or go to a museum and draw them live.