If you already own a DSLR, buy a star-tracker and use it to determine whether the hobby is for you.
You will also need to invest in image processing software, either generic (Photoshop) or specific AP software (PixInsight, AstroPixelProcessor). This will get you into the hobby for a few hundred bucks. If you don't own a DSLR, buy a cheap second-hand one - with a decent prime lens. Any focal length between 14mm (for Milky Way) and 200mm (individual objects) would work, depending on your interest.
The next step starts to get expensive, and will depend on whether you want to take images of planets, wide sky fields and/or deep-sky objects (galaxies and nebulae).
Easier way to go is either experiment with different prime lenses for your DSLR, or buy a good quality - ideally triplet apochromatic - refractor with 70-100mm aparture and focal length between 400 and 600mm. The refractor will also need a good-quality mount - rated to carry the load (for AP, its around 60% of the quoted load rate) . The mount is actually the most important part of the setup.
For example, I graduated from DSLR + sky-tracker to SW Esprit 100 and EQ6-R Pro mount - at a total cost of t a few thousand $$. [Less than $5000]. You also need to include extras like power supplies, automatic focusser, Raspberry PI controller etc of you want to make your life easier.
That would be my recommendation.
