This is costly especially after you factor in interior repairs for the mold damage.

The website looks cool but they do not show pictures of the interior of the house.

Administrative CostsBldg permits/applications$1,200.00Land Development CostsSurveying/Site Plan$5,000.00Sewage access$55,000.00City tap-in fees$6,150.00Building Development CostsFeatureSingle UnitPer Quad% of totalFoundation$6,497.09$25,988.359%Floor Structure$8,662.78$34,651.1312%Wall/Exterior Finish$8,662.78$34,651.1312%Roof & Cover$7,218.99$28,875.9510%Window/Doors$3,609.49$14,437.975%Interior Finish$5,775.19$23,100.768%Floor Finish$3,609.49$14,437.975%Interior Features$3,609.49$14,437.975%Bath Detail$2,887.59$11,550.384%Kitchen$5,775.19$23,100.768%Electric$7,218.99$28,875.9510%Plumbing$8,662.78$34,651.1312%Total:$70,073.64$288,759.46100.00%Location Factor (1%):$70,774.38Two Story Adj. (2%):$72,189.86* figures calculated using the 2020 National Building Cost ManualAssumed overrun:5.00%Number of Quadplex:3Total estimated budget:$976,942.29As you can see, the total budget would be roughly $1M.

Much damage, particularly the interior, comes from poor tenant behavior and damages. 

One parent (Guarantor) has endless requests: Can we repaint the entire interior, or at least the bedrooms?

If you decide to rent it out, you'll have to screen tenants very carefully, and critically important:  do regular detailed inspections of the exterior and interior of the subject rental.Fix any issues immediately, and make sure the tenants know they must contact you if there is even a small problem.  

Ex: chandeliers, glass interior doors, doors that jams, and floors that aren’t sealed down. 

It cost me 2k to paint interior.

@Charles Seaman it will be more minor renovations... interior and exterior. 

There are areas on the exterior that have raised shingles where the nails have worked there way loose and causing the shingle material to be raised as well as moss and debris present which can allow for moisture issues on the interior .2.