I'd say other issues (aside from the very important transit one already raised) are things like power redundancy/quality and cooling:
Ok, maybe cooling you can sort out relatively easily, and if you only have one or two servers it might not even be a major issue to start with. However, it'd be some work to get your house electrics supply cleaned up nicely for a server, get yourself a decent UPS setup including appropriate redundancy, and of course a generator which fires up automatically in the event of a power outage (with a decent stock of fuel handy too).
How's your inert gas fire suppression system and VESDA? That's also assuming that your house also has 24/7 security with biometic access control?
The bare minimum requirements may be relatively painless to setup (e.g. buy 1 x cable/SDSL connection or whatever) but to maintain quality and therefore uptime you should expect/demand of a proper datacentre facility is pretty much setting up a mini DC in your spare room - i.e. probably not worth it compared to the relative small colo fees for using a fully equipped facilty.
All of that said, it really depends what you're using it for. If you just want to put your old 286 "server" to use hosting your hobby static HTML site I'm sure you can get away with using a reasonable ADSL connection and accepting the limitations of having it hosted under your desk
- It'd be alot cheaper to colocate your server in a data-centre.
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