I'm wanting a good mic for recording an acoustic guitar in my home studio. Everything I read says the SM81 is the way to go. But at $350 new it's a bit more then what I can spend. Can anyone recommend a few decent alternatives?
The SM81 is a classic "small-diaphragm condensor" microphone. Search for this term on Sweetwater or other pro-audio store site and you will find that it is a densely populated space.
The SM81 is a popular mic that has been around a long time, so you can probably find one used for a bit cheaper.
To stay with new mics, you can find something like the Audio-Technica 450 for about $250, Rode NT5-S for a bit over $200, the Avantone CK-1 for about $150, and on down the scale. All of them have something to offer; GearSlutz will have a boatload of opinion about any particular one.