My Real Estate agent believes that they can be sold together since it's a single deed... 

Just be sure the calculate in the interest you are paying on that HELOC into the new project.As for banks, my experience has been that many banks do not like to do HELOCs on rentals unless you have a decent portfolio which they then look at as a business instead of a single rental property.

Own few condos and single family now looking to expand into multi family 

nearly every single applicant will tell me their pet is either ESA or Service dog.  

Try to buy after 1950 and avoid single family conversions.

Most people will never own a single investment property.

I suggest starting with a  smaller single family property, and build from there.

It's a flexible approach, suitable for both single-family homes and multi-unit properties, and can be tailored to fit your lifestyle and financial goals.It's important to research local housing laws and market conditions to ensure a successful house hacking venture.

As you pay off the debt are you comfortable with $4M equity exposure within a single LLC?

It’s written explicitly for investors to help them understand rehab projects and budgets.