When you are lending, make sure to allocate about 40% of what you earn to potentiale defaulters. About 1 in 8 defaults.
You can take all the precautions you want, but you cannot predict every single defaulter. There is a reason the rate is 10% and not 5% or 2%. It is not because it is possible, but because the lenders are taking a big risk.
If the loan is with no-collateral or BCTalk accounts, the first thing you should do is to ask for a signed message.
Badbear has said the burden is on the lender if the account is hacked. The same goes for no-collateral loans, you will lose 100% if it happens to be hacked.
1.
Never take Passports or ID as valid collateral. Always something which you can obtain value from again. (Selling ID is a no-go)
2.
It depends on borrower. The collateral should
always 100%, unless it is a no-collateral loan. If the coverage is less then 100% and the collateral drops in value, you could quickly lose a lot in case of a default.
The coverage should preferable be above 120% and in most cases above 125% to 130%.
Why? The collateral can change in value and if it is a newbie requesting the loan, he might default if the value drops below 100%.
But all of that is logic and common sense.
Few things to look out for;
Big loans have a smaller default rate. If a sufficient collateral has been put up. They are the safest if they are taken with collateral.
Smaller loans takes more time, but provides a better interest. What is the difference between 0.002 and 0.004 in interest? Compare it to 0.02 and 0.04. People are more willing to pay bigger interest.
When that is said, they have a bigger default rate. Accounts can easily be farmed up and defaulted on.
I hope this answered some of your questions. I would recommend to start with 0.1 BTC and then see if it is something you want to continue with.
EDIT:
As you have no trust feedback yet, I would recommend to get help from an escrow. I can provide my help, but not with big amounts. (max 0.5
BTC)
Instead, I would recommend people like Zazarb for Cryptocurrency, SebastianJu for other stuff and ranochigo for Bitcointalk accounts.