They must be NEET or housewives because they are able to come to a place like this in the middle of the day.
Only people who are NEET or housewives could come to a place like this during the day.
zoroさんのように They must be .... because ~ の形を使って言うなら
1) They must be NEET or housewives because they are able to come to a place like this in the middle of the day.
「昼間からこんなところに来れるなんて、ニートか主婦に違いない。」
のように言えます。
または Only people who are .... could ~ を使って言うこともできます。
2) Only people who are NEET or housewives could come to a place like this during the day.
「昼間からこんなところに来れるのはニートや主婦くらいだ。」
ちなみに「ニート」は NEET - Not in Education, Employment or Training または Not in Employment, Education or Training（学生でもなく、仕事にもつかず、専門的技能を学んでいない）の略になります。
ご参考になれば幸いです！
日本 
