I set up a 13 gallon low tech reef tank for the first time late last year( it's currently June 2024). I started it with a Tetra Nano HOB filter, a no name 50 watt heater and the cheap LED lights that come built into the plastic aquarium cover. I even cycled it on dechlorinated tap water! Done in 3 weeks. It has progressed since then to some more advanced equipment but it doesn't take a whole lot of parts, time or money to get started. I'd be willing to wager that a person who knows where to look could get up and running for $50(used tank and equipment of course)
Disclaimer: It will not stop here. Soon you will be an expert on most all available equipment, practices and livestock. Be prepared to embark on an arduous journey if you take the plunge. Good Luck to you if you do!!! It's worth it!!!