This is what I have heard done:
Call in your phone book any local PI. Ask him what to do! Also call PI in the other town. Ask what evidence he would require from you to hand to the OBS when they are alone.
This is their main job...taking pictures of infidelity, but ALSO TELLING THE BS!!! They will have some good ideas for you.
In my town, the PI said he would get a DVD together. Then I would hire a PI in the other town to hand deliver to the OBS when he is alone. This happens all the time! This is their job.
In my town here were the 2 PI's I called. One, a lady said 500.00 for 10 hours.
THe other, a guy said 1500 up front that he puts in an escrow acct. When he has all the documentation, he gives me a detailed report of the charges and returns back the rest of the $$$ to me.
Also, you can make a free consult with an atty, tell them you are thinking about a divorce. Tell him you want to do the PI thing and who do they recommend. They know good pi's because they have to go up against them in court all the time!