Fancy furniture in a house full of babies and toddlers...

I know from the title it doesnt seem like a real issue, but here's the thing...have any of you ladies been able to successfuly teach your little ones to stay out of a certain area of the home - without gating it off?!

My husband and i bought a house with my mom. We've all lived together 2 years now. The house is a good size as we plan to have 3 or so children down the road. I'm currently pregnant with our first, due in May.

Our "formal" living room has been unfurnished the entire time because my mom insists on saving up to buy her "dream" furniture for it. Well she finally saved up enough to order just 2 couches and 2 chairs. The set cost $15,000!!! I can't imagine how much more shes going to spend on tables and other decor. The minute she is anticipating getting money she spends it before she even has it. I sometimes worry about her retirement since she has $0 saved for it (but whatever i let her live her own financial life, she doesnt seem stressed)

The actual problem i have is i cant even imagine having little kids and constantly worrying about keeping them out of that "fancy" room. I want to gate it off but she keeps saying a gate will ruin the look of it and that we can train the kids to be clean or not go in there. I doubt we'll be able to teach them to be "clean" because when a toddler takes a blue marker to a white couch they're not being "dirty" they're being CREATIVE! I dont think she remembers what it's like to have little kids.

So im wondering... have any of you ladies been able to successfuly teach your little ones to stay out of a certain area of the home - without gating it off?! Any tips or expectations i should have?