PS: My strategies work even if there is an invincible guy. The repairmen will repair the damage he inflicts instantly. Just make sure not too many ppl get to ur house. Then the repairmen will start to be not enough.
Even better strategy for "THIS IS SPARTA." Buy the NoobTube/Grenade Launcher and upgrade everything to the max. Then buy walls until your house has 200 or 300 hp. Then spend the rest all on repairmen. If you still have extra money, buy some (useless) gunmen, or an UZI or something.