Breh, how are you talking about having a side chick when you don't even have the balls to let her know she's going to the side chick?
Also, what you mean you live with your girl out of convenience? You mean you live with her out of "I can't afford my own place." I see it all the time, people date and get spots together not out of desire to share a space together.....but on some "neither of us can do it alone but we can afford this together" type sh#t. This constitutes a
MAJORITY of live-in relationships, so you're not alone.
If you feel the need to "date" this chick just to have her around and you're trying to make her your side chick, then you're already setting yourself up for an explosive loss. The type of loss that will leave you homeless and in shame.
Now, if you said you're trying to have a girlfriend #2, then by all means date her, build a foundation and bring her into the fold on the polygamous level. But you're trying to have her as your side chick.....that's a different animal. The kind of animal that she needs to be clearly learned upon and know exactly what the situation is, so she doesn't catch unnecessary feelings and/or blow up your current relationship.
You can't "date" a side chick and expect it to be functional....side chicks don't get treated like women you "date"....they're side chicks.....they get sex and some laughs and then they get the door.....and they know this. If this chick doesn't know this, then you should leave her alone and find a chick who is down for that role.
Peace