For someone without a degree or without a degree in a computers-type field, certification can be very helpful. It depends, though, as not all certifications are created equally. Generally, look for something on an established technology or field, or with an established school. So Microsoft or Oracle is good, or Java programming or Project Management is good, but if there were such a thing as PHP certification, it might not be so good, at least not right now. Some certifications require classroom instruction (Oracle does).
Certification classes are not cheap and they are no guarantee of a job, but they are a measurable statement of your qualifications. Plus, tuition is deductible if you itemize your taxes. You'd need to look at salaries (see
www.salary.com or look in
www.monster.com) and also look at current opportunities.
If the software you want to study is only mentioned in a handful of job openings across the country, that could mean that it's a rare skill and employers will pay well for it. Or, it could mean that it's a skill that's on it's way out of favor, or that it's been replaced by something better or that it's an idea whose time has not yet come. If what you want to study is more common, it will mean more opportunities and you'll have a better chance of getting a job, particularly if you aren't tied to one geographic area, but at the same time it also means there is more competition so salaries could be lower.