Even if you don’t have budget for paid search, Google Adwords is an incredibly useful tool for an early stage startup. With a budget of just $100 a week, you can not only validate ideas (are people interested in our product idea?) but you can also learn the language of your customers – i.e. do you get more clicks when you talk about “shiny report tool” or “fast report tool”? http://www.verticalresponse.com/blog/5-ways-to-use-paid-search-seo-together/

https://www.searchenginejournal.com/14-best-paid-search-seo-tools/118689/