I would not put any length limit on myself. A post can be 2 sentences or two pages. What matters if it makes an impact. Also, you can easily kill the lack of content with pictures. Sure, the more words, the better you will do with the search engines, but you can always add a few quotes from others. Just make it quotes people are likely to be interested in.
Once you get visitors to come back, you will be able to capture a loyal audience and in time as content builds up and IBLs age like fine wine, you can control a nice resource and add information as needed.
But you can always hire someone to come up with something and even if people will not find it interesting as something you may write in a moment of passion, the search engines will eat it up, and if you brand your blog well, it will still be able to serve it's purpose. Always ask yourself about your end goal with the blog and then go from there.