Yes, Pathfinder recomends that
The cost to research a new spell, and the time required, are left up to GM discretion, but it should probably take at least 1 week and cost at least 1,000 gp per level of the spell to be researched.
But the corresponding section in PHB 3.5 reads only
A wizard also can research a spell independently, duplicating an existing spell or creating an entirely new one.
And that's it. No costs, no time for research given. Everything is up to DM with no guidelines.
But there are lots of ways to hand out spells for wizards. You can have a powerfull wizard with lots of spells allow your PC to copy spells from his spellbook. The general guidelines for it are
In most cases, wizards charge a fee for the privilege of copying spells from their spellbooks. This fee is usually equal to half the cost to write the spell into a spellbook (see Writing a New Spell into a Spellbook). Rare and unique spells might cost significantly more.
So if you want to give the wisard access to spells via research it is reasonable to have these costs. Or you can set the cost equal to the price of a scroll. Whether you give it via research or from another wisard or any way is only a matter of how you roleplay it, not balance.
At the same time in the DMG 3.5 at page 35 we read
Introducing an unbalanced spell does more damage to your game than handling out an unbalanced magic item.
Handing out any spell the player wants can be disbalancing, no matter how you roleplay it. If you are going to run a low money campaign, you have to be even more cautious about handing out spells freely, because nonspellcasters will have a more limited access to resources.
If your PC can get any spell from an NPC wisard he can get the same by research for the same price without breaking the balance. But mind what spells you give, no matter how you roleplay it.
- You can give wizard spells for free. It doesn't contradict the rules (at least 3.5).
- There are several ways to give wizard spells described in the rulebooks. They have different prices for a spell and times for copying, but they have no other restrictions. While you take prices and time from one of these and roleplay it the way you like, you are not breaking the balance.