You are partly right. Doom did have another property that was briefly seen in FF #193. It was a mansion that served as an HQ and lab complex for a Cynthian Associates. When the FF had to split up in FF #190-191, Reed needed a job. Sue went to work on a movie financed by Namor and Reed took a job at Cynthian Associates. If Reed had known that Doom's mother's name was Cynthia, he might have caught on to the real owner of the company