@Ningsi
Old places come with old things - old water pipes, old electrical wiring, old sewage, old mold & bugs.
Newer places come with newer stuff - which can also include newer toxic chemicals in the wallpaper, glues, furniture, etc.
Your best guide will be your own nose, your own eyes, and your own ears - be meticulous with each sense and trust your feelings. Most real estate agents are best relegated to background noise or elevator music - ignore what they say - any imbecile can become a real estate agent here - it's part of China's social responsibility - employing those with unmarketable job skills to keep them off the streets (and from stealing my bicycle...'nother thread).
Quiet is critical with kids. Check out the locations during the five major peak human traffic periods - morning, lunch, and late afternoon rush hours, dinner time, and somewhere around 10-12pm at nite.
Look at parking (regardless of vehicle ownership) for both cars and e-bikes. Cars indicate the socio-economic level of the neighborhood. A plethora of e-bikes generally indicates a plethora of somewhat lower skilled to unskilled laborers - a potential burglary risk.
The level and quality of restaurants in the area similarly indicates the general mood and night life of the area...and restaurants are bug and rodent ultra-mega-super magnets.
If your desired location is a newer high-rise with an elevator - check out the elevator during rush hours. Check the elevator make - if it's foreign, the place might actually be quite nice. If the elevator is domestic - the builder went cheap - you should expect a plethora of miniscule but incredibly annoying and time-consuming problems to surmount. Older places - hope you like stairs and nosy neighbors.
Bluntly, a rental contract rarely means anything in China and especially in Kunming. This is why most landlords prefer advance payment of the contract in full. The disadvantage - hot water issues, broken toilets, plumbing, wiring issues - all at your own expense. FYI - that big ol hunkin tank in the bathroom is most probably an electric water heater. For a large family - you'll have to stagger your bathing times, bathe together, or opt for an on-demand gas heater which is virtually infinite (as will your gas bill be)...but - dirty gas fouling the heating elements requiring monthly to quarterly service - it can be more effective for larger families. FYI - most gas heaters have an auto-shutoff timer - so you'll have to be careful when, for example, filling the bathtub. Also - fouling of the heating elements accelerates the auto-shutoff - sporadically...and increases your gas bill exponentially.
Cooking and heating gas in older places is toxic. You'll occasionally notice stenches in the kitchen similar to that of burning tires or similarly toxic rubbish. If the kitchen is electric - better for families.
As you're family enabled - unless you opt for a car with the inherent parking, theft, and vandalism woes - you'll probably want to opt for an e-bike (as opposed to turning your husband into the grocery mule). Surf the gokm threads on the wonders and woes of e-bikes. They remain high target theft items - but my bike store tells me mountain bikes (like my last TWO) are the highest theft of convenience item, for those looking for quick pocket money.