The decision to tear down an old house and replace it with a modular one depends on various factors, including the cost, zoning regulations, the condition of the foundation, and the overall value that it adds to your property.

If the cost of repairing the existing house is higher than starting anew with a modular home, and the zoning regulations allow it, then tearing down the old house and building a modular one may be a more cost-effective and efficient option.

However, it's important to consider the value that an old, historic house may add to your property, as well as the impact it might have on your community. A modular home may not have the same architectural or historical significance, which could affect the value of your property and the surrounding area.

It's recommended to consult with a professional builder, contractor, or real estate agent for a more informed decision.

Zoning regulations are set by local governments and dictate how a piece of land can be used. To find out the zoning regulations for a property, you can follow these steps:

1. Contact your local government: You can start by contacting your local government's planning or zoning department. They should be able to provide you with information about the zoning regulations for your property.
2. Check online resources: Many local governments have online resources that provide information about zoning regulations, such as their website or GIS mapping tool.
3. Review the property's deed: The property's deed may contain information about the zoning regulations for the area.
4. Hire a professional: You can also hire a professional, such as a land use planner or surveyor, to review the zoning regulations for you.

It's important to note that zoning regulations can change over time, so it's a good idea to check for any updates before making any decisions about your property.