Live Rock Purchase Questions

I am in the process of setting up a new tank and its time to get some live
rock. A friend is takeing down his tank of a few years due to lack of
interest and whatever else. He has offered to sell me his live rock at a
good price but he has let his tank go abit the last few months and all the
live rock is covered in red algae. Now the rock is good and cured and his
livestock is doing fine but I would have to deal with the algea from what I
have read.

My question is should I get this live rock with algea or just get some rock
from another source that is algea free for my new tank?
How hard is it to get this rock back in shape and whats the best way to do
so?

I guess I would like to know the pros and cons and any advice in between
would be great. Obviously I am new to the hobby.

G.