I am a small business strategy consultant, with loads of experience working with startups, like yours.
What kind of coaching are you doing? Is it something you need to do in-person, or can it be done by coaching over the Internet or phone?
The Internet is a fabulous way to do things at a low-cost. Not only to actually provide your service, but also to market it to a large audience.
If your business is something you need to do in-person - then make sure you use the various low-cost options available to you online to get yourself a presence. There are tools, like wix.com, which will allow you to build a free website and give potential customers a way to find you and contact you.
Also, if you are an expert in your field, make sure you are blogging and getting your information out to the public as frequently as possible. This will increase your ranking in search engines and make you appear like a true thought leader.
If your coaching can be offered online, make use of free tools like Skype - and embed them within your website. You can take customer payments through Paypal and similar cheap online systems.
There are many tricks to launching a low-cost business. Many depend on your specific requirements. Feel free to give me a call via this service if you want more information.