I am trying to say "When one person has a loss, another could perhaps benefit." This is what I have: Quand une personne a une perte, une autre peut-etre pourrait profiter a la perte. Was I supposed to have used conditional? And do you notice any errors?

If you mean "... could perhaps benefit from the loss.", then you would say "...profiter de la perte", or better still, "...pourrait en profiter." where "en" stands for "de de perte".

You could also say "subir une perte" to mean "suffer a loss". (note: subir is the infinitive form, third person singular is "subit").

You can use the conditional here to express something that could happen

You can use the future as well ( to express something that will happen)
EX… une autre pourra profiter de la perte
peut-être (spelling)

To improve your sentence and make it clearer, you can rewrite it as follows: "Lorsqu'une personne subit une perte, une autre personne pourrait éventuellement en bénéficier." Here are the changes explained:

1. "Quand" vs. "Lorsqu'": In this context, "lorsqu'" is a better fit because it emphasizes the temporal aspect of the situation ("when"). "Quand" tends to be used when referring to habitual or general situations ("whenever").

2. "Personne a une perte" vs. "Personne subit une perte": Instead of using the verb "avoir" (to have), it is more accurate to use "subir" (to undergo/suffer) to convey the idea of experiencing a loss.

3. "Une autre peut-etre" vs. "Une autre personne pourrait éventuellement": To express the possibility of someone benefiting, it is suggested to use "pourrait éventuellement" (could potentially) rather than "peut-etre" (perhaps). Additionally, adding "personne" after "une autre" makes the sentence clearer.

4. "Profiter a la perte" vs. "En bénéficier": The expression "en bénéficier" is commonly used to mean "to benefit from it." It is more idiomatic than "profiter à la perte" (benefit from the loss).

Regarding the conditional, it can be optionally used in this sentence, depending on the intended meaning. If you want to convey a specific condition or hypothetical scenario, you could add the conditional mood. For example: "Lorsqu'une personne subirait une perte, une autre personne pourrait éventuellement en bénéficier." This implies a hypothetical situation where one person might suffer a loss, and another person might potentially benefit from it.