I ordered a grow tent through GrowAce.com but there are many out there. The Dealerz.com has a lot on there but look around for specials on many of the sites. Sometimes a great price doesn’t equate to quality. Google "indoor growing tents and you will have plenty to choose from.
A grow room is really nice because you contain the smell in the tent and having a charcoal filter to clean the air is a big plus. How big a tent depends on the number of plants you want to grow, your space to grow in and the need for stealthy grow that contains smell.
I used a 2x4x5 foot grow tent and it worked great. I didn’t even need to vent it that much until flowering. That is when you really need a good fanand filter. The “smell of success” may be cool to you but it can also lead to problems if the neighbors or guests in the house can smell it!
Good luck on your grow