Your biggest asset when becoming an internet marketer is to know how to get free targeted traffic to your web sites. It doesn’t matter how many web sites you’re promoting. Your primary goal should be to keep the cost down. It feels great to have monthly sales well into the thousands, but it also can ruin your day when you realize that most of this money goes right back into your advertising costs.
Yes, there’s a rule that you need to reinvest 75% of your profit into advertising and marketing. I like this rule, but it also needs to be timely constraint. I think this rule is good for your first 3-6 months of business. After this you should be able to pull back the cost for advertising without impacting your income streams.