Don't go into debt buying hardware. Start with one card and use your profits to expand your rig for as long as it's profitable. Also, get solar power (nearly free electricity) and set up the exhaust from your rig to heat your house in the winter (and if you're clever enough to build a condenser ... cool it in the summer).

In all seriousness, I do ok with NiceHash using just "spare" computing power on my primary machine, so if you build a dedicated anything and keep your power costs down you're in decent shape.