Could I fund the purchase using a bridge loan with the assumption to sell my existing home ($1.5M)? 

You can do a subject to transaction but that is not legally assuming the loan.the banks got rid of assumable mortgage long time ago. 

Take a look at BP's blog where new articles are published every day: https://www.biggerpockets.com/blog4.

Start systematically reaching out to these businesses to let them know you are a buyer and give them your criteria.  

@Mindy Rosscup, you want a contract that is specific to the laws of your state.

Some states allow the owner to hire employees to work on their behalf.

You should talk to a few bankers about options.

Some lenders may also want to see law and ordinance coverage in your insurance and perhaps a rebuild letter from the city stating that the property could be rebuilt as a residential 4plex if destroyed. 

@Samantha SueroWelcome to Bigger Pockets.

Is it possible to talk a few mins?