Look for a deal
Many formalwear shops offer package deals for wedding groups—for example, a discount on the groom's tuxedo when three groomsmen rent. Shop around for a special offer or a discount that makes sense for his group.
Keep it basic
A black tuxedo coat with a waistcoat and bow tie is still the most versatile, inexpensive option whether he rents or buys. And the good news is that this outfit will look just as great in your wedding album in 10 years as it does today.
Do the math
If he's going to be renting a tuxedo with any amount of regularity, it usually works out to be less expensive over the long term to buy a well-made traditional tuxedo. The cost of renting formalwear is usually about one-third to one-half the cost of purchasing, so calculate the options.
While a lightweight linen or seersucker suit is a dapper look for daytime spring nuptials, it will look completely out place for a December wedding in Vermont. One in medium-weight wool is a more versatile option.