My future husband runs his own business and his income is irregular. How do we plan our finances before marrying?

Plan based on the slowest month, not the busiest one. Ask for a picture of his income over the past year, including the weak seasons. Make the average of those low months the basis for maintenance (nafkah) and the household budget. The surplus in good months goes into a buffer fund to cover the leaner months. Also make sure business money and household money are kept in separate accounts, because mixing them is the cause of many misunderstandings. Ask too about business debts and who the guarantor is. These questions are not a sign of distrust, but a sign you are serious about building a household. An honest entrepreneur will appreciate questions like these. See family finances.