You must have the required stats for all of the quests and also leave about 200-300k in your inventory for any quest items needed. I will price the service based on how many quests you need completed.

For a full completion of every quest in the series it will cost $25 or 24m 07

Considering some of the quests are a lot longer than the others i.e. underground pass, regicide.
the shorter quests will be a smaller reduction from the cost of the full service while the bigger ones will be a larger reduction. For example, if all you have left is regicide, you will pay $10/9m 07 instead of the full price

Cost of each quest
Regicide:$10/ 9m 07
Underground pass: $10/ 9m 07
Biohazard: $2.50/ 2m 07
Plague city: $2.50/ 2m 07