Depending on the size tank you want to start with you can do coldwater tank right fairly inexpensively.
If you're interested in the aggregating anemones then a tidepool style tank would be a great idea IMO

Keep an eye out for a small frag tank, even a used one, since the majority of them are built shallow and rimless with thick acrylic. You can pick one up on eBay shipped for about $150, but I bet you can find a used one for half that
Only other larger expense would be a chiller, but if you go for a smaller sized tank you can use a smaller sized chiller which are generally less expensive as well. I've got used a 1/10 hp on a 1/2" thick 40 gallon and maintained temps in the mid 50's easily. I currently have a 12x12x12" coldwater nano that runs on a 1/13th hp chiller at 59F, total system setup cost me about $300 and the monthly electricity usage is only $6 according to my kilowatt meter on the system.
Don't be discouraged by anyone saying coldwater is expensive or hard to find livestock. The costs for setup are pretty much the same as a tropical marine tank, the livestock is usually priced about the same, it just takes a bit of research since its still fairly new to most home aquarists.
Hit me up with any questions you might have
I'll message you about the aggregatings anemones, I think I have a few in my personal tank even if they are out of stock
