well depends on what kind of content & call to action have on your website. and it also depends on your promotion. let see if your promotion is good then you can get high ROI with spending extra $$. this is my personal experience.
Its minimum cost for seo is USD 1200 per year..........and roi may be 5000+ depend on your products and services which your are selling..............
ok and what if i just have an ad sense account from where i can earn that it. and if i m using multi revenue Programs? . what will be the minimum and maximum budget i need ??
You're asking how long a piece of string is. The minimum budget is zero, but some of your time to learn how to seo and promote your site. I'm not sure what the maximum is exactly, but I know a couple of the top agencies charge $20,000 a month. Most people using adsense make less than $20 a month