Before they are famous, many seiyuu would work part-time whether it be at fast food restaurants or even physical works. For example the seiyuu Uchida Aya:
During the early stages of her career she supported herself with part-time jobs such as being sales staff at departmental stores, production line quality inspector at factories, and sometimes even menial labor carrying cardboard boxes. The key criteria she had in choosing her jobs were that they had to be shift-based and versatile such that she could report to her entertainment office any time she needed to.2
Others also have career as eroge seiyuu (Nitta Emi, voiced a character in an eroge, Da Capo III), before they went famous and might continue even after they are famous, such as Itou Shizuka and Asakawa Yuu.
Like all entertainment job, a seiyuu job has its peak, and after that peak is over, the number of job offers one receive would reduce. I'm curious as to what does a seiyuu that is no longer at their peak of fame do for a living when they no longer have many anime to voice? Do they work on eroge? Or just normal games? Or they turn into salary-man/woman (office workers)? Please give some examples with your answer.
If they retire at age of 40 or so (which is already stretching it as most female seiyuu would see the peak of their fame at their 25s, while the male ones would still be able to retain their fame longer), then they still have around 30 to 50 years of life ahead as a retired seiyuu. Certainly they would still need some jobs that earn them money to support their living, which is what this question is about. This is especially true since seiyuu don't get royalties from having their voice recorded, unlike singers. Mangaka gets their royalties from every copy of goods that is produced from the series they make.
krazer suggested that they are like athletes and other celebrities, they retire. Many athletes continue working after they retire from their professional career. Some famous footballer becomes a coach, for example, Zinedine Zidane, Antonio Conte, Diego Simeone, Pep Guardiola, and many more. But as for seiyuu, I never heard of a seiyuu that turned into a voice-acting coach.
senshin suggested that they do Hollywood dubs, while Aki Tanaka suggested that they do freelance voice-acting and voicing for mobile games. Problem with this is that as Aki has mentioned, it is not regular, while their living bills (accommodation, food, etc) still needs to be paid regularly. And with the seiyuu being no longer at the peak of his/her fame, freelancing might not be enough to earn them the money they need. Also I don't think the number of such job available is not much. I mean how many hollywood movies are being dubbed into Japanese anyway? I bet not much. Only the famous ones would see itself being shown in Japan. As I noticed from games such as Chain Chronicles, Kancolle and Panzer Waltz, one seiyuu voice several characters in such games.
Thus, I think the number of jobs available from dubbing Hollywood movies and mobile games won't be that much, and they still have to compete with seiyuu that is still at the peak of their fame, plus the rookie seiyuu as they are often also chosen to mitigate the production cost.