Can churches be used for secular purposes?

This question is not directly covered in Scripture. Perhaps a better question would be to ask is whether or not a daycare facility in a church can glorify God. Depending upon the local laws in a jurisdiction (cf. Rom. 13:1-7), I think it may. While there are many things a church building shouldn't be used for, I personally see no problem using parts of a church building as a daycare facility throughout the week. Let me explain.

First, a brick and mortar building is not the church of the living God, nor is the building holy in and of itself. It’s simply a structure where people gather for worship. It is the people of God — the body of Christ (cf. Eph. 5:25-32) — in worshiping assembly in the presence of the Trinity that constitute the church (cf. Eph. 2:19-22).

Second, the early church had somewhat of a reverse situation. The church gathered “from house to house,” and I can image many of these had children (cf. Acts 5:42; 20:20; 1 Cor. 16:19; Rom. 16:5; Col. 4:15; Phile. 1:2). Children aside, Christian homes in that era (and this one too) were used for many things — schooling, businesses, cooking, caring for the sick, etc.

Third, a daycare facility may be a ministry in and of itself. It is an opportunity to lovingly care for children and share the gospel (cf. Matt. 19:14; 28:18-20). Moreover, it is an opportunity to assist parents who must work (cf. 2 Thess. 3:10). These can be godly ministries.

Ultimately, there are many things to consider in opening a daycare facility and, as with most things in life, it will present certain challenges. But if a church can do this, and do it well, then I don’t see a problem. I consider it as a matter of Christian liberty (WCF Chapter 20).