My thoughts are if there is a war in a system, you could pay like a million credits to support a faction in war state and you will be paid back with interest depending on how much you pay for it.
Yea like having the rating of the faction like their influence over the war change the value of bonds?You should be able to invest in Minor Factions, and those Minor Factions should then benefit from the extra assets.
This could be through gifts (monies in exchange for reputation or influence), loans (repaid over time), or bonds...
For reference: Bonds pay back a fixed amount at regular intervals (annually, quaterly,...) to the Bond-holder until they reach maturity, at which point the full face value is returned to the holder. The term of the bond may be years (up to 30 or 50 years). They are therefore different from a loan which would be repaid over the term with compound interest.
However, for the holder to receive anything from a Bond it of course requires that the Issuer can pay. So holding a Bond is not risk free -- especially war Bonds. This is where a country's credit rating matters, and Minor Factions would need the same.
Trading bonds represents a large market place -- where the value of a bond is determined by the amount that can be earned by holding it (compared to other assets over the same period), and the credit rating of the issuer.