Short term study visa - using property sale as proof of funds

You are going to have problems.

1. As Giacomo Catenazzi says, selling a property to pay for your trip is a bit of a red flag. In fact any large amounts of money suddenly appearing in your account, or the account of someone who is paying for your trip, is going to be a red flag. You have to make sure that your documentation of the sale is rock solid - a legal document showing all details of the sale, and as much other documentation as you can raise. The agents will definitely make thorough checks of the documents.
2. If your father is paying for some of the trip, then you absolutely must include information about his finances. They will need to know that he can afford to make the payments. The land sale isn't enough on its own - maybe he had debts that he needed to pay out of the land sale. If his business didn't use a bank account then you will need to find some other way of showing that he has both the savings and the regular income to afford the payments. Maybe tax statements, or accounts from the business.
3. You said your father didn't use his bank account for savings? Where did he put his savings? Where is the money from the land sale? If it is in your father's account, and it's the only thing in that account, that's going to be another red flag.
4. If your father really has no record of his finances, it might be better to use only your brother-in-law as sponsor. But you can do that only if your brother-in-law can genuinely afford to pay for your entire trip.

Selling property for a travel is not seen well. You sell properties when you want to emigrate, so break link to home country.

Regular income is much better. And you should try to stress on documents which prove you will return after the course at Oxford (maybe also describing advantages of your course on your career on your home country).

Whoever you use as a sponsor has to prove that they can afford the commitment. You don’t say how much the overall cost of the proposed short study course will be (travel to UK, course fees, personal spending during the course etc) but however much that is, your sponsor needs to show:

• the money is available to you

• the spend is proportionate to their income/savings

• the source of the money.

Whoever sponsors you will therefore need to provide pay slips (if employed) and bank statements covering a 6 month period. If there are any material unusual transactions during that period, they’ll need to provide evidence of where the funds came from.

If you haven’t already done so, you should read UK visa refusal on V 4.2 a + c (and sometimes 'e') The answer there covers pretty much every angle of what you need to consider when applying for a UK visit visa.