Bitmain so far is the only Bitcoin miner maker that sells to the Public on a regular basis. Once again they are sold out.
Avalon *is* taking orders and should start shipping their miners Nov 21st. In the past they have been trustworthy.
There really are no other reputable Bitcoin miner makers -- but there ARE a lot of scammers so beware!

1st rule of mining: NEVER spend money you cannot afford to lose. If you have spare cash to spend then think of it like a vacation at a casino. Maybe you will make money, maybe not.

2nd: ONLY buy new miners direct from the manufacturer or their authorized distributor as-listed on the companies website. It is the only way there will be any Warranty on new equipment. It is also the 1st step in avoiding scams.
https://Bitmaintech.com for s9's
https://canaan.io for Avalon miners

3rd: If starting out 'to learn' then look for a used s7. Much more manageable in terms of noise and reliability. Also a helluva lot cheaper that the s9 is.

On the heat: Plug in and run 2x 1,250w heaters in the room for a day. If it stays a comfortable temp you would be fine.