100Mbit is way more than enough, unless you are trying to break into the adult industry or similar.
The problem with doing it at home is usually the reliability of network and availability of network, ventilation, and the reliability of power. But if you have some 100Mbps FTTH then sure, buy a UPS and rack up a server at home. Make sure it's in an area that doesn't get much warmer than you would like for yourself (whatever you do, /do not stick it in the closet./ )
Really, the colder you can keep it the better, but you shouldn't have any real problems through 80-85 degrees (I'd like it cooler, but eh.) I've worked in home-made data centers like that where the temp. regularly hit 100 (F, not C) and things mostly worked.
Do the math on your power usage, though; many places have retarded pricing for residential power, meaning you could actually save money by bringing it to a data center.
Me, I'm stuck on a 3m down, 768M up connection or something like that. Wholly unsuitable for actual hosting.
