Does anyone know a way to connect 4 guitars (electric, acoustic, bass and mandolin) to a single bass amp? We`re only playing in the house so doesn`t have to be flash, just cheap!

You would have to find a amp with 4 input ports, obviously. I have only heard of amps with 2, so you may have to go to an instrument/sound equipment store and ask them about that. You might have to spend some money, man.

Money, whats that, no money here.
I`ve done some research and apparently you cannot plug a guitar straight into a mic/line level mixer and then output to the guitar amp. The guitars each have to go through a DI box. Is this true? Otherwise I could have just bought a cheap mixer and my world would be a happier place

nah its not going to work because even if u ran it thru a mixer, u wouldnt be able to get any volume out of the guitars.

ur taking the Watts and basically dividing them up between the 4 of u.

u can use stereo equiptment for the "Lighter" instruments. use a $2 radio shack adapter to put a line into an aux input, and play thru the streo speakers.
stuff like that.

plus its a bass amp the acoustic and mandoline would sound terrible.

i also thought u can run them thru ur computer, mic in or line in. but im guessing that u need it for a gig and thats out of the question??

leave the bass on the bass amp, a bass on anything else will blow that thing up.
find an old stereo reciever and some speakers and try not to blow them up.