Level 5 characters should have about 500 gp of wealth, with 1 or 2 common magic items and an uncommon mix of consumable and permanent. A good guideline is that there should be at least one treasure per PC level awarded. At the beginning of level 5, they should have approximately 700 gold each and, at the end, 3000 gold each, so they earn a total of around 2300 gold. You enter a d4 number depending on your class.
You'll then multiply that roll by 10 to get your starting gold. Monks are the only exception to the rule. Due to the equipment rules of the class, they shoot five d4s but do not multiply them. With a small percentage of players reaching the highest level of games, many DMs may be surprised by the prospect of D%26D's high-level game.
It's a completely new skill set, and many argue that D%26D doesn't actually support it. Once you get to level 12 or so, the characters start to mess up the system. And when most DMs flinch, you'll find plenty of opportunities to shine. My practical answer is that I give computers enough gold to achieve something interesting and useful, given the equipment and gold they have now.
If you misunderstand this table and think that it's about the amount of wealth you'll have per level, you'll end up in a strange situation where from level 1 to 4 you won't win any gold and, on level 5, you'll win 500 + 1d10 * 25 gold. One option to determine your starting gold is to get a gold reserve and use it to buy your initial equipment.