Are rents really that high that people would pay $700/mo for a very small bedroom and shared bathroom in Mira Mesa? Probably not I’d guess, I know there are still 2/1 places by the beach for $1400, and then the kitchen is only shared between 2 people.
Did you save all that money so you could live in house with a kitchen shared with 3 adults and a bathroom shared with a stranger?
Get one roommate. The quality of your one roommate who has his own bathroom is also going to be higher, with less stress for you, than trying to have three of them there.
The single highest return on investment on home renovations is supposedly replacing an ugly front door with a nice new one. Is your front door already newer and nice?