How will cooking/cleaning be managed?
Who will claim living room on a evening?
Do you enjoy doing similar things on a evening eg tv/music?
What time will 3 year old get up? Where will her toys live?
Does your brother have a similar level of cleanliness to you?
Will your brother and gf want alone time in the house?
Will you and your dd be asked to babysit?
Is you dd clean /tidy/respectful? If no will that be an issue?
Will toddler routines/tantrums cause issue?
What time does toddler go to bed/get up?
How will house hold costs be managed ?
What happens if you meet someone?
When not working will you hang out or do your own thing?
Can you and your dd cope living with a three year old,?
In theory it's a great idea but if it goes wrong your all screwed as you have left your affordable rentals for this. Id think hard and be prepared to discuss every potential issue you can think of in advance so there's no nasty shocks.
Id want two living rooms so you can hang together or separately depending on how you feel.