About income, soldiers got payment monthly as any other profession, so as many soldiers/or more ranked ones, you get, more you gain.
machines also give gold because of the crew, but spent resources to maintain their mechanism.
about combat
Keep in mind that a soldier with packs of explosives can sneak throught houses and plant charges around armored vehicles, run and detonate the charges. So a soldier well used and correctly equipped can destroy a whole armored platoon.
Again about cities, the urban warfare is far different of field ones ( believe me, i'm on a semi closed military program of my country. so i keep a military and a civillian life at same time). So a lot of tanks are very imponent, and if they spot enemy soldiers they will toast then in a flash. BUT city narrow streets and a lot of hidding spots guaranted by the buildings give a fair advantage to a inteliggent soldier. Also civillian bridges and streets aren't proper to heavy war machines. Some heavier ones could'nt use these ones or they could ruin the bridge, or destroy the street, difficulting the terrain advancing.
Also, if the idea is become realistic, some tanks shot about 11 Kilometers far of their position, or even more if the tank is quite modern. So tanks could be used as mobile artillery ( well they are mobile artillery at all

) and don't put on the frontlines as many games show.
The "shield" function tanks with both anti-personel and anti-armored weapons that come in front with the soldiers are of different aplication.
the M-113 like, with light weapons and support material to troops in other hand can be a constant, as it increases the troop duarbility and so on.
Tell me if you like my ideas, and soon a i post here some others.