A two day job with a net due in 45 .... RUN unless you are completely broke or this job is going to set you up with a couple of years of guaranteed work and a severe penalty to them if they break the agreement. Can you go to a restaurant, enjoy the meal and then send them a check in 45 days? Chances are more than 99% that this client is going to be a grinder that will turn your 2 day job in to a two week ordeal with changes and re-dos and that they will then complain about your work to everyone they meet. It's not worth it.
When you freelance, unless you want to be nothing more than a day laborer, remember that you are in charge. If they are not willing to meet you on your reasonable terms you will a slave to their every whim.
In most states a sub contractor can, ans should ask for a deposit from a new client. The limit is usually something like 10% up to a maximum of $1,000. The guy putting in your new lawn is going to ask for that. You should too unless it's a government agency, which seldom give deposits, or a major corporation with an established and published procurement procedure.
Only when you get these details worked out should you move to the contract phase and you should be the one submitting it. Things are different if it is a network from a job posting, but if you seek find the client or are referred to the client, it should be your contract, not theirs.