It is obvious that a person loses income by not working on Ḥol Ha-mo’ed, as every day on which he does not work he loses the earnings of that day. This is not truly a loss (davar ha-aved), though. Rather, it is missing out on profit (meni’at revaḥ). Therefore, hired workers and independent contractors must take off from work on Ḥol Ha-mo’ed, in order to free themselves to enjoy the festival and study Torah. Even if a worker normally makes 1,000 shekel a day, and has been offered double to work on Ḥol Ha-mo’ed, he may not work. The command to rest is applicable to rich and poor equally. Similarly, if a carpenter is offered double to build a cupboard on Ḥol Ha-mo’ed, he may not do so. What is at stake is not his losing money currently in his possession, but rather his missing out on making more money.
In contrast, a person who is likely to lose money or property that he already owns may do melakha to avoid this. The goal of prohibiting melakha is to allow a person the peace of mind to rejoice and study Torah. One who is worrying about losing his money can neither rejoice (Ritva) nor focus on Torah study (Raavya; Maharil). Additionally, the Torah cares about our financial wellbeing. If a person is unable to take care of urgent issues with his business or fields for seven consecutive days, he will end up suffering losses (Ha-manhig).
Therefore, a vineyard owner who has ripened grapes ready for picking may pick them on Ḥol Ha-mo’ed, if not doing so will lead him to suffer a serious loss (SA 537:16). If one’s home or store was broken into and the door is now broken, or if one’s alarm system has stopped working, he may have the repairs done by a professional if he is worried about thieves (SA 540:4). Similarly, if a pipe burst in a home and there is a concern that the home and furnishings will sustain water damage, the pipe may be fixed by a professional. If a person has merchandise for sale, and he has a well-grounded concern that if he does not sell it on Ḥol Ha-mo’ed he will not be able to do so afterward and will lose what he spent on it, he may sell it on Ḥol Ha-mo’ed. However, if he would make a profit on it after Ḥol Ha-mo’ed as well, but a smaller one, he may not sell it on Ḥol Ha-mo’ed. Such a case falls into the category of missing out on profit rather than suffering a loss (SA 539:4). If by not working on Ḥol Ha-mo’ed a person will lose the source of his income for the upcoming months, he may work on Ḥol Ha-mo’ed. This is because losing one’s source of income is considered a major loss (rather than missing out on profit).
In addition to the first principle we set forth, we must add an additional principle: Even when a loss is at stake, the permissibility of work depends upon the size of the loss and the difficulty of the work. To avoid a small loss, the Sages permitted only a melakha that can be done quickly by anyone, or craftsmanship that can be done with a shinui. Time-consuming or very demanding work is not permitted. To avoid a medium-sized loss, they permitted skilled labor of medium difficulty. To avoid a major loss, they permitted even extremely difficult work. The difficulty of the work permitted should be proportional to the magnitude of the loss. After all, melakha is permitted to avoid loss so that a person will not be sad on the festival, negating its mitzva of joy. Accordingly, if a great deal of work would be necessary to prevent a medium loss, it is better to enjoy the festival and ignore the loss. However, if what is involved is a major loss, which would prevent a person from enjoying the festival, then even extremely hard work is permitted.
In cases of uncertainty, the decision about whether to work on Ḥol Ha-mo’ed can be made by thinking about what one would do if he were on vacation when the problem arose. If the anticipated loss is great enough that the average person would cancel a family vacation to prevent it, then one may work on Ḥol Ha-mo’ed to prevent it. If the loss is not significant enough for a person to cancel a family vacation, but is serious enough that he would work on the issue for a few hours during vacation to prevent it, then he may work a few hours on Ḥol Ha-mo’ed as well. If it is a loss to which one would be willing to dedicate an hour during vacation, it can also be worked on for an hour on Ḥol Ha-mo’ed.
This decision is also dependent upon the person’s economic situation. Someone poor will work during vacation to avoid a loss of a few hundred shekels because it would be a big loss for him, while someone wealthy would not bother. Of course, this needs to be evaluated based on the habits of an average person, not of someone so lazy that he would always prefer vacation, nor of a workaholic who would cancel a family vacation for the slightest reason.
This rule is the most complicated of all the rules of Ḥol Ha-mo’ed, because one needs to evaluate honestly the degree of difficulty versus the degree of loss. In cases of uncertainty, a halakhic authority should be consulted.
At first glance, it would seem that even if a person is risking the source of his income for upcoming months by refusing to work on Ḥol Ha-mo’ed, he still may not work. Preventing the loss of future income which has not yet come his way would seem to fall into the category of missing out on profit rather than avoiding a loss. Nevertheless, since he would be losing his set source of income, it is in fact considered a loss, and he may work in order to preserve it. This is addressed by the poskim in the context of a big fair (SA 539:5; BHL s.v “ve-afilu”; see BHL s.v. “ve-im” on SA ad loc. 9). This is also the rule for one who is likely to be fired (SSK 67:11).
What if someone is living in somewhat difficult circumstances, and a business opportunity falls into his lap? If it will make a nice profit, even if not a huge one, he may take advantage of the opportunity, as long as he makes sure to dedicate a part of the profits to festival expenses, so that this deal will contribute to his enjoyment of the festival. In contrast, if one is wealthy and can easily buy everything he needs for the festival meals without taking advantage of a business opportunity, he may not take it up (SA 539:4).These permits could be explained as applying only to business, since they do not involve melakha intrinsically. This explanation is the second opinion of Raavad quoted by Rosh (MK 1:28; see BHL 533:3 s.v. “mutar”). However, it would seem there is no fundamental difference for these purposes between business and other forms of melakha. Rather, the primary criterion is the level of difficulty involved, as Raavad explains. The rule for a number of isolated business opportunities is the same as for unskilled labor – both cases are permitted in order to allow the purchase of holiday food. In contrast, opening up a store is considered absolute melakha, even without taking into account specific melakhot, because the sheer effort involved is full-fledged work. Only if there is a possibility that he will lose the source of his income is he permitted to open a store (Ramban; see BHL 539:5 s.v. “eino”; see also below section 7 and Harḥavot).