I’m no expert but I have done a good bit of work studying lead
contamination / remediation issues when my young children tested with
very elevated blood lead levels after moving to an old house.
There are quite inexpensive lead test kits sold in hardware stores,
They do work after a fashion, but the results are strictly binary
(Pb=0 Pb=1). This may be all you need. Another limitation with these
kits (the ones I saw at least) is that they are only really suited
for testing paint chips. If you have a lead problem it often
originates with the paint but is manifested in the dust. Lead in
paint is not harmful as long as it isn’t ingested, when the paint
deteriorates and the lead is in the household dust there is an easy
path to ingestion and poisoning.
Now that I’ve said all that, you want to test for lead in old solder
joints, don’t you… If that is the case, never mind. I have nothing