Думаю, "real" - это указание на наличие какого-то имущества которое предоставляется в качестве обеспечения исполнения основного обязательства / гарантии.

Personal guarantee = "личная" гарантия, то есть некое договорное обязательство гаранта, в соответствии с которым последний гарантирует исполнение должником основного обязательства, при этом не предоставляя имущества в залог (no collateral)

Real guarantee предполагает "гарантию" исполнения обязательства должником в виде предоставления некоего конкретного имущества в качестве обеспечения.

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http://www.google.co.uk/url?sa=t&rct=j&q=real and personal g...

It is important to distinguish between real and personal guarantees. Personal guarantees are contractual obligations of a third party, and they act as if they were external collateral. However, they do not give the lender a specific claim on particular assets, and change the actions he could take in the case of the borrower’s bankruptcy. Consequently, only empirical analysis may help
distinguish which of the two types of guarantees (real and personal) has a stronger impact on the loan interest rate.

...... Our second interest rate model is estimated for firms and producer households, but not for consumer households because loans to consumer households are mainly mortgages that, as said, have to be assisted by real collateral.....

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http://in.answers.yahoo.com/question/index?qid=2010050402052...