FlexJobs is 100% legit. While it may not be necessary for everyone, if you have limited time available to dig around on the internet and vet companies for legitimacy it’s well worth the investment. They research each job lead to make sure it is truly remote or flexible and it isn’t a scam. I’ve had a membership for a very long time and find it well worth the small investment.
If you have never been self-employed before you need to do some further self-assessment to determine whether you have the right personality to be an entrepreneur. Starting a business is not for everyone. (See 6 Traits You Need to Be Self-Employed.) Common traits for successful business owners are motivation, self-reliance, perseverance, initiative, and the ability to deal with uncertainty.
Concentrating all marketing efforts on a small but specific and well defined segment of the population. Niches do not 'exist' but are 'created' by identifying needs, wants, and requirements that are being addressed poorly or not at all by other firms, and developing and delivering goods or services to satisfy them. As a strategy, niche marketing is aimed at being a big fish in a small pond instead of being a small fish in a big pond. Also called micromarketing.