Those are pun-based catchphrases for the job search service by the name of サーチ.
First of all, 「あれ」 is the imperative form of 「ある/有る」; therefore, it is a verb. In case someone is wondering, this 「あれ」 has no relation to the 「あれ」("that") as in 「これ/それ/あれ/どれ」.
In fact, the two 「あれ's」 are even pronounced quite differently -- 「あれ{HL}」 for the verb and 「あれ{LH}」 for the demonstrative pronoun.
「Noun + あれ」 means "Let there be [noun]!"
One of the nouns that are most often used in the expression above is 「幸{さち}」 ("happiness"). So, for instance, 「君{きみ}に幸あれ!」 means "Wish you happiness!", "Much happiness to you!", etc. To the newly weds, we often say 「お二人{ふたり}に幸あれ」.
Now, 「サーチ」, as in searching on the internet, sounds sort of like 「幸{さち}」 except for the length of the first syllable, which makes this pun work. You are turning the common phrase 「幸あれ」 into an advertisement catchphrase 「サーチあれ」 for the job search company.
"Let there be Search for recruiting staff!" ← 「求人募集にサーチあれ。」
"Let there be Search for job-hunting!" ← 「仕事、バイトさがしにサーチあれ。」