Making hirable npcs to work for free/for item

[Bonaccorso]

I've got an idea to make a type of hirables based on BaseHire.cs (I'll make new CustomBaseHire.cs), who will work not for money but for something different.
Now I'm trying to figure out three cases:

1. How can they work for free? Now they are hired when given gold, so it's likely has something to do with changing "public override bool OnDragDrop(Mobile from, Item item) " and there it's hiring for gold, and adding hiring code to some other place - but here I'm confused for where can it be put?

2. For item; it seems to be easy in theory - I plan to try to remove the lines from new CustomBaseHire:

 // Is the item the payment in gold
                    if (item is Gold)
                    {
                        // Is the payment in gold sufficient
                        if (item.Amount >= Pay)

And - then how can I change the number of days in which he's gonna serve? For example, making it infinite?
Likely removing the part

                                NextPay = DateTime.UtcNow + PayTimer.GetInterval();

                                PayTimer.RegisterTimer(this);

and this check as well?

protected override void OnTick()
            {
                var list = Hires.Where(v => v.NextPay <= DateTime.UtcNow).ToList();

                for (int i = 0; i < list.Count; i++)
                {
                    var hire = list[i];
                    hire.NextPay = DateTime.UtcNow + GetInterval();

                    int pay = hire.Pay;

                    if (hire.HoldGold <= pay)
                    {
                        hire.GetOwner();

                        hire.Say(503235, 0x3B2);// I regret nothing!
                        hire.Delete();
                    }
                    else
                    {
                        hire.HoldGold -= pay;
                    }
                }

                ColUtility.Free(list);
            }

Did I miss something?