It can be done, but only if super good runs, and tight BRM..
If you play the huge freebies, with hundreds of entries, the payout is slim: $50 prize pool, often min payout is .05 or .10, for 2 or three hours of effort.
BHig entry freebies, if you take big chances, combined with a lot of luck,and a lot of time invested to get to the money you can get to the final table, or close to the top ten, where the
real money is.
Scan all the freebies at all the sites you play at; cherry pick those that have best return.
Stay as far away from rebuy freebies ifyou can. The rebuy is usually way more than the min cash.
To build a BR, you have to be smart with BR; use it wisely, sparingly. No cash games. Use BR for set entry tournies, and sit and go's; the most money you can lose if your entry; cap your losses.