You could take a look at the webactions module. There you have readCookie and setCookie javascript activities. You can use those in a nanoflow.
You can customize your SessionTimeOut and KeepAlive in the settings -> Configuration > Open your config and customize the constants;
https://docs.mendix.com/refguide/custom-settings/#general
You could also add an attribute to the house entity, generate a unique ID and send this to the user (can also be a deeplink, a clickable link to the specific data). Somewhere in your app create a 'Open existing house' where the user can give the unique ID to get the existing house. With this you prevent that you'll have a lot of sessions open (This depends ofcourse of the amount of users).