All of the above variables matter. There are also other issues - eg close to a house, crops, dams etc. A few are absolute no-go but most simply involve compensation to the farmer. Many farmers do not realise that they only hold title to their land to a depth of a few metres, and that the State, not the farmer owns the mineral rights. So the State is really giving a right to the miner to exploit its resources, but under the conditions it sets.
It varies so much between States that I doubt if general advice here would be useful. Usually Mines Depts. will give honest information if asked by a landowner, and there are also organisations that can give advice (eg in Victoria the Farmers and Miners Association). Take a map with you - if they can see the location it saves a lot of talking. Usually the farmer must sign some sort of access document, and it will stipulate some sort of compensation and the type of work permitted (eg $ per drillhole or per metre drilled) and if they refuse it can go to court (some of which are not expensive - eg mining wardens court). Sometimes farmers find it economically worthwhile to work with the company, particularly if there is water that might be intersected during drillings, and it saves costs. While large companies know the law and are unlikely to try something that they are not legally entitled to, small ones are often not as well informed, and if they make unreasonable demands they will end up paying costs in court etc. However often it is best to just be informed what to do if it happens, but sit back and do nothing until it does happen.
My experience is that landowners often get ulcers worrying about things that never happen. And the odds of a mine being discovered are very small (one in a few hundred at best). Sometimes companies prefer miners kids as field techs - they know the area, kow how to work and like an income in off-seasons - and the farmer knows that any land rehabilitation will be done properly.
Sadly there is always the occasional company that is a pain in the backside - but most don't want any aggravation themselves.