Visitor visa documents query - Help please!

[rohwan007]

Hi everyone,
Really appreciate the great work everyone's been doing on this forum.

I have a query re visitor visa application for my cousin. For context, I (ILR holder) will be hosting him in my residence during his entire stay in the UK which is 11 days.
So, he's a medical student back home and wants to visit us and travel around UK during his term break. He himself will be funding his visit. He's currently unemployed and full time medical student but manages to find security flaws within multinational companies apps, websites and other platform (like Apple and Facebook) which he gets paid bounty for his finding (so it's not a regular form of employment).
So his savings of about £12k is entirely from his bug bounty payments from Apple and Facebook.

Recently applied a visit visa for him which was rejected and the following points were outlined in his refusal letter:
1. You state that you are unemployed and have not declared any other sources of income
within your application form. The information provided does not demonstrate the income or
finances of any close family members in your country of residence who may be supporting
you financially. The information provided in support of your application therefore does not
establish your financial circumstances to be as declared or confirm how you are supported in
your country of residence.

2. I acknowledge that you have supplied a document that advises that you currently have an
income through Apple and Facebook. However, the information currently available to me
does not demonstrate how this income is generated, or the level of regular income that you
currently receive. I am therefore not satisfied that you have provided an accurate account of
your economic circumstances and this undermines the credibility of your application which
leads me to doubt your intentions or that your personal circumstances are as declared.

3. You state that you wish to visit your cousin and that they will provide
accommodation and maintenance for your stay. I acknowledge a letter from your sponsor.
However, using the information currently available to me there is no evidence of any
previous contact between you and your sponsor and it is not clear why they are supporting
your visit. The documents provided do not establish your relationship with this person and it
is unclear how you are related. I am therefore not satisfied that you have a genuine personal
relationship with your UK sponsor or that they are able to provide you with support for the
intended duration of your stay.
The information you have provided also does not demonstrate what personal or financial ties
you have to your country that would ensure you leave the UK at the end of your proposed
visit. On the balance of probabilities, I am not satisfied that you have demonstrated that you
have ties to your home country, or country of residence which would encourage you to leave
should you be granted entry to the UK.

Following documents were submitted:
1. Sponsor's BRP and passport + Letter from land registry, Council tax bill + cover letter confirming his stay
2. His last 6 months bank statement
3. Letter from his uni confirming his enrolment and term break
4. Payment invoices from Apple and Facebook
5. Cover letter explaining his situation
6. His passport

His tuition fees and any other expenses are currently paid for by his mum which we did explain in the cover letter. This trip, he'll be supporting himself with his savings though.
Now, in the new application, in addition to what was submitted previously, what other documents shall we submit? I can't think anymore than his mom's business registration and business bank statements, and land registry document.

Thanks in advance

[secret.simon]

Also see the advice in this thread for the chances of a single, unemployed male applying for a UK visit visa.