Homebrew Spell-research

Main
A spellcaster of 5th level or higher may use spell research to gain access to spells that he does not have access to from scrolls, spellbooks, or (if a divine spellcaster) his deity. Spell research costs 1,000gp, and takes two weeks of research, per level of the spell. A cantrip takes two weeks and costs 1,000 gp.

The DC to research a spell equals 10 + the level of the spell you are researching. You get to add your spell attack bonus to the roll. The research DC for a cantrip is 10.

Example: Pyro is an 8th level sorcerer researching wall of bones, a 4th level spell. It will take 8 weeks and cost 4,000gp, and has a DC of 14. With his +7 spell attack bonus, he only needs to roll a 7 or better to succeed.

A spellcaster can only research a spell if he can still learn spells of that level. A cleric or other divine caster can only research a spell with the permission of his deity (DM’s discretion). The deity will usually remove a spell of the same level from the cleric’s spell list in exchange for granting the new spell.

Libraries
To research a spell, a spellcaster must have access to a library. Wizard’s guilds and major temples often will provide their wizards and clerics access to such a library. If a spellcaster wishes to compile his own library, a minimum of 4,000gp must be invested to allow research on 1st level spells. For each subsequent spell level to be researched, another 2,000gp must be invested.

Having an exceptionally large library aids research. For every 10,000 gp of value above the minimum required for the spell, the spellcaster receives a +1 bonus on his magic research roll (up to a maximum +3 bonus).

Every time a wizard successfully researches a spell, 10% of the gold spent for that effect is added to his library value, reflecting the value of books purchased, notes, and annotations made during research.

Authoritative tomes or rare books found as treasure might provide an additional bonus to research specific spells or types of spells.