With housing an a company's value you're really getting into world-speciific questions that are hard to generically answer. In my world, the answer varies from realm to realm. There are only a handful (2-3) that have companies of the sort you're talking about, and many of those are royal monopolies (so it's hard to say just how much they're "worth" in that sense since they're backed by the treasury of the realm). Some of the overseas trade companies that have escaped royal control (for now, at least) would value in excess of 5 million silver (I run on a silver standard), but they only have a handful of locations and make their major coin when they resell what they import. The royal monopolies import at least double that value.
Value of a home is also subjective. In the major port cities that are home to the trade houses mentioned, houses are expensive (especially if they're in a "good" quarter...upwards of 100,000 silver with attached grounds and walls), with prices dropping off as you move further inland. More rural realms can see a similar cost, but that's for a small walled keep (needed in the less populated areas). There are also some places where a home couldn't be bought for any money (dwarven clanholds) and need to be inherited.
To get back to your army question, if you take a normal soldier's rations as trail rations (1 bp per person for a week at town cost, according to ChL), you'd be spending 500 silver (50 gold) a week to feed 5000 men. Switching to standard rations cuts that cost in half, but increases the weight. Keep in mind that's just for the fighting men, though. Most armies had an assortment of camp followers (tradespeople, merchants, gamblers, persons of ill repute, and so on) who would soak up supplies and cause problems for commanders. And with your cavalry, if you're looking at heavy horse (knights), you'd have more than one horse per knight (at least one for the squire, and a riding horse for the knight in addition to his warhorse), which increases the forage requirements and need for blacksmiths.