Basically it is not really possible to run a combined CAR 30 & Part 145 Maint org on the same premise. The 145 requirements will not allow CAR 30 stuff in the hangar, the documentation would be tricky but hard to keep separate.
Lets say 2 LAME @ $100K each, 1 apprentice @ $30K, 1 office staff CAR 30 @ $50K & 1 Part 145 office staff @ $60K (CAR 30 will assist 145 with paperwork).
That is $340,000 a year in wages only. So if 2 Lame and 1 appy do a C402 and a C210 hly a week (4,600 flown hours a year) = $10,000 a week in income at best in labour.
46 weeks a year = $460,000.
Now cover rent, insurance, workers comp, power, water, manuals, tooling, phones, office equipment, transport, fuel, bad debts, bank fees, computer programs, staff mistakes, etc.
Then the appy is away a lot and staff get sick.
You can save $60K by not doing 145, but is there the work for 4 staff or even the 5?
(Ball park figures)