The general rule of thumb for HID lighting is 35-50 watts per square foot. A 1000 watt HID fixture in a 5’x5’ tent would put you at 40 watts per square foot - right in the middle. You will want a good air-cooled fixture with multiple angles on the “back side” like an Xtrasun 64 in a tent of that size. You could also do a pair of 600 watt HID fixtures, or a pair of CMH fixtures.
The “high cost of HID lighting” really depends on the cost of electricity where you live. I did a cost analysis of LED vs HID 6 months ago (based on the average cost of electricity in the U.S.) where you can see how long it takes to break even. You can read it here:
Don’t get me wrong - I love LED lighting and have plenty of it, but many people can’t afford them and there’s nothing wrong with HID lighting. I would much rather see someone get an HID light than be convinced they have to use LED, then go purchase cheap blurple lighting from Amazon.