Buying a clone of existing website adds nothing to it. If you really want to start something new then make sure it is new. I would go with custom solution from ground up with different features. Otherwise just buying a clone of a website is just going to be a marketing nightmare when it comes to market your product once it's launched.

Based on your description of the app I would suggest that you need some users before you can even plan for charging them. Once you have some initial users they will do the word of mouth marketing and help you spread the word faster. So take in account the money saved in marketing. Charging or not charging also really depends how much cash your company has and how much longer your startup can survive without making any money from it. Whatever is the time estimate, deduct 3 to 6 months from it and start charging. Timing this is the essential part of the strategy.

I have been working online since last 2 decades and it has its pros and cons. As they say "The grass is always greener on the other side of the fence." Anyway if you want to start out then there are plenty of opportunities. You should make a list of things that you would love to work on and once you have made up your mind on something specific, you could acquire knowledge for that subject with online courses and tutorials. (Because working from home gets boring real soon. But that is a whole new subject for the psychologists) For example: I love programming and all so I went into web development. It also included designing and technically I could use Photoshop but I am not artistic with colors and drawing. There will be such things for sure in any line of work you choose where some things will be better than the other. Just choose wisely.