You can likely expect a lot of VT multicolors without any specific patterns, more so just washes of different colors. Not very appealing in the world of betta sales. Bettas can have hundreds of fry. It's a lot of work, and not something to rush into. Make sure you do your research, and have everything prepared before you try. You can mate brothers and sisters, but as chesterscot stated, this is usually done if you're trying for a specific line-- e.g. yellows or mg. Too much inbreeding can lead to genetic problems, but that's usually not seen until F8-9, but could be earlier due to different variables.