Feedback from a complete indoor novice:
Yes the closet size is good for two plants. I've read grow journals on this and other sites with many more than two plants growing in smaller spaces than that. So long as you can fit a pot in the bottom, some lights at the top and have 2-3 feet or more of space in between then you can grow. That space looks nice and tall so it should be easy to get two plants in there without much effort. There are many ways to make the plants grow to fit the size and shape that you want. Google 'micro SOG' for examples of 20+ plants growing in smaller spaces, just as an example. If you wanted to you could grow a single plant and train the branches in such a way that you could fill that space with flowers, though in general going with more plants will fill your space quicker as there's less vegging time involved.
You don't need the fans yet so long as the space is cool enough. You don't want your little girl born into an oven. The purpose of ventilating the space is to get the heat out and to let fresh air in so the plant can breath. As there's no plant mass yet the only thing to worry about right now is not baking your seedling.
Apart from that the only thing I would say is to plan ahead. Work out how many lights you're going to have in there and how you're going to get the fresh cool air in and get the smelly warm air out when the plants are fully grown. It will be much easier to do rough tests on your ventilation and temperatures now when the space is empty than it will be when the space is full of plants. If you add lights and fans piece by piece as you go then there's a risk you'll make a mistake at some point, make the space too warm by adding one light too many, and fry the plants overnight.
Good luck with the grow
