I've researched that some individuals will build, put the build in a 30-year mortgage with a bank, pull out the equity and repeat the process in another build.

Also, It can’t be subdivided and the duplexes won’t be able to be sold off individually.

This applies to house hunters for construction crews (or high-value individuals), insurance claim relocation specialists, and nursing contract placement coordinators. 

Why not invest in a fund or syndication vs. a single individual?

There's pluses and minuses to each choice....For Financing, the HML here in the states always drop and restart their Foreign National Programs. 

The choice between maintaining liquidity versus reducing debt will largely depend on your priorities and future investment plans.As for subdividing or CPRing the property, there are several advantages.

If you do this, plumb and wire each one to the individual units to keep your costs down.

As a GC I can advise try to retain control of your finishing material orders (anything where you need to make a choice ((tile, flooring, lites, faucets, tubs)) vs. construction materials (2x4s, mortar, shingles)) because we get those discounts on the finishing items and we keep them!

Going with a S&P 500 fund can be a safe easy choice.

The social engineers (lawmakers and their special interest handlers) stifle and discourage growth, individual liberty, and confiscate property (your hard earned income), they are absolutely crazy.