How soon should you secure your midwife

How soon are we securing our midwife? I would love a home birth and identified what midwife I would like, I was looking over the contract and the retainer is $1,500 non refundable.

I’m 4weeks 4 days and had a chemical pregnancy in January so just nervous.

I did do hCG and it 5x in 70 hrs so that is at least reassuring but if I pay now and miscarry next week or the week after I’m just out the money? Or do you all wait until 8 weeks before securing your midwife I also don’t want her to get booked out with someone else not sure how this typically works?

Also I hate hospitals so I don’t want one but is it normal to still worry if you are making the right decision or not?