Most affordable would be high quality cotton prefolds with a cover. You can either pin them or use a "snappi" to hold them closed, and they work great. Only downside is that they may intimidate your husband. Since you're at home, you don't need to worry about daycare providers. Otherwise you can go with a "fitted" type diaper - these are similar to the prefolds but have elastic at the legs and waist and usually snap instead of being pinned - you still need a cover though.
I agree with another poster - the reviews at www.diaperpin.com are VERY helpful. There are many more expensive "systems" out there like pocket diapers etc, but the prefolds are definitely eco-friendly and economical. They cost $1.50 to $2.00 each and you'd want about 24 of them so that you can wash every 2-3 days. You probably only need about 3 covers - maybe 4 - and those will cost you around $10 each. I like the Motherease airflow ones, though there are many to choose from.