Initially (when I started in this hiring business a mere 4 years back) insurance for SFH on my 120 had no limits for hrs on type or total hrs and a fixed £2k excess (plus, for you, an added 'loss of business' compensation payment of about £1,000 if the machine was down for a while). All we had was a review of flying skills and license before deciding to accept / reject the work opportunity.
First warning sign came with a SFH (a very, very experienced pilot with military and civilian turbine but low-hrs on type) starting incorrectly and creating a 4-second over-temp just 2 degrees C short of "engine toast". All SFH pilots were then monitored for "first start" at the field (though after that they were on their own) on each hire. No insurance impact from that event, fortunately.
Then the machine was W/O which the insurer paid out on. On renewal they changed the terms & conditions. New requirement for total hrs 200, hrs on type 50 OR CPL(H) with less hrs (can't recall) on any turbine and type-rating for EC120. Safety pilot required below these hours. In addition, the excess was increased to £75,000, reduced to £25,000 (regardless of hours) with a safety pilot on-board.
After a few months I changed insurance companies, but the options are for insurance are rather limited in UK.
Now there is no longer an insurance-company specified minimum hrs or safety pilot impact on excess. BUT..... who can SFH is negotiated individually as one more bent airframe = potentially uninsurable and out of business (for both my aircraft).
Much, much choosier now about who flies her and whether they can go without a safety pilot. She therefore does have some 'solo' SFH work. From my viewpoint, as owner, the additional business income potential must balance with the additional risk that I (unavoidably) take on from that hire. My 120 is remarkably busy at present (touch wood!) so it is paying its way.
DMW2007 is right - we all want sole pilot P1 not the cost / space / weight of a safety pilot. Therefore I think it is worth checking with the business whether they will solo SFH the machine to you (when qualified) before you go for type rating training. I would say (personally) it is better that you do the type rating training with the guys who will provide what you want after qualifying - they will be more sure of your abilities.