Mermelstein 's business endeavors are operated through One & Only Realty & One & Only Holdings and provide family office planning services .
One & Only Holdings specialize in the representation of foreign buyers in the acquisition of high - end properties worldwide .
Mermelstein 's business endeavors are operated through One & Only Realty & One & Only Holdings , which specialize in the representation of foreign buyers in the acquisition of high - end properties worldwide , and provide family office planning services .