There are many freelancing websites on the internet that you can use to get clients. Even the software houses these days create profiles in the freelancing websites to get more clients. Fiver and freelancing.com are very popular websites for starting a freelancing career. Freelancing.com is better than Fiverr because people sell services on cheap rates in Fiverr. If you manage to create an account with good reviews on freelancing.com and Fiverr ,then you will be able to earn a very good income. For increasing the rating of you profile in freelancing.com, you can participate in the contests. The contests will give you a payment if you win. The contests are from lower prices to higher prices. You can choose the one that satisfy your needs. You can slowly build your reputation and then after some time you will start getting some clients.
UpWork is also a good website for freelancing. You can use Upwork and freelancer.com website to find more clients. Since you are an seo, you can also create your own website and add a "Hire an seo" Page in the website, then you can optimize your website to receive clients and it will also give your more visibility in the searching engine.
The problem with those methods is that they do not reach the most targeted audiences. Let’s say you find a business with a few ads in the phone book. Call the phone book company and find out how much they charge for those ads. If the amount is reasonable for an online strategy, put together a sample plan and present it to the business owner, explaining how their current spending could help them reach targeted customers who are ready to buy. The math will do the selling for you in most cases and the client will be glad for the ride into the future.