Wow a lot of replies in a short time…
First the guy has nothing and is asking about a kettle so “fermentation control” is crazy past where he is. I have been brewing since the 1980’s and other than using a heat wrap to boost a bit in winter I have NEVER had any “fermentation control”. Refrigeration only came in in the middle of the 20th century so most beer historically has not had fermentation control. Not saying it’s a bad idea but just not pertinent to this topic.
Kettle wise you do not need a “fancy” kettle and I would not recommend one with a sight tube for wort, that will be a bugger to clean.
You need at least an 8 gallon for a five gallon batch but I would argue with others that you are better off with a 18+ gallon kettle. The reason is you have room to expand and with 5 gallon batches you are pretty much boil over proof. And it doesn’t cost a lot more.
Other than pride (and you should take that in to account) there is very little functional difference between the cheapest kettle you can find and the most expensive. Thick bottoms are great for stews and such but you are boiling water (essentially) so very limited advantages. I have a pair of 8 gallon pots I got on sale from my LHBS for ~$30. I use them alternately for brew pots and fermentors. I have a 18 gallon pot with a sight tube and a thermometer that I use for a HLT. I got it for ?!$40- $50 bucks on sale, and it replaced an aluminum pot I got used for $25. I replaced it because it was too small (7 gal), the aluminum scare has been pretty solidly debunked. And I have a 6-7 gal pot I got at a Chinese grocery a long time ago. It’s taller so less of a boil over risk. All but the last I bought with a 1/2" coupling welded on. The first pot I drilled a hone and added a bulkhead coupling and a valve, but I had brewed extract with it for years just as it came from the store.
BUT what I would do first is join whatever homebrew club meats closest to you and then ask about gear. The chances are really high that someone has a pot they have out grown and would be willing to sell it to you for a lot less that a new one would cost. That is how I got the aluminum HLT and it’s how I will pass it along.
The other thing is I would look at some of these all in one systems. You were going to drop $200 on a pot but for $300 you can get a “mash and brew” and that will let you get off the stove and do all grain (save a lot of $).
Something like this
https://www.homebrewing.org/10-Gallon-1-Weld-Volume-Marked-Brew-Pot_p_6065.html
would work well for $60 or this
https://www.homebrewing.org/15-Gallon-1-Weld-Volume-Marked-Brew-Pot_p_6066.html
for $90
RoboBrew $350
https://www.homebrewing.org/Robobrew-All-Grain-Brewing-System-925-Gallons_p_7485.html
or Mash and Brew $300
https://www.homebrewing.org/Brewers-Edge-Mash-Boil-All-Grain-Brewing-System_p_7497.html
I just posted links to one of my LHBS so buy local if possible. I have seen cheaper prices for some of these items but it was easy to use my LHBS links. I don’t work for them and the links don’t put anything in my pocket, they are just for reference.
Hope that was enough disclaimers…
Your local Home Brew Club is the best place to start.