Well, to be really honest , an indoor cat needs much more attention than an indoor/outdoor cat, due to the fact the cat would get bored without you being there, & would be sleeping a majority of the day and you will see it gain weight overtime due to the stress of being alone & bored. Which could also cause a lot of health problems such as UTI's & stress which may cause it to have diarrhoea.
Because your cat is a single cat of the household & us inside all the time, he/she will need you more, cos it won't have contact with other cats...thus causing it to think it's one of you (human)...so, i would suggest, best thing to do is, get two, if you are gonna be out a majority of the time.
It will make your cats life much more easier cos it will have its own kind to spend time with.
Well, best wishes & congratz.
Kitten & experience.