Is it legal to sell a home with a cesspool?

Yes, but any cesspool serving a property subject to sale or transfer with a closing date on or after January 1, 2016, must be replaced with a septic system or other type on On-Site Wastewater Treatment System  or connected to a sewer line, if available, within one year of the closing date. http://www.dem.ri.gov/programs/benviron/water/permits/isds/pdfs/cessfaqs.pdf