It may come as a pleasant surprise, that to send a standard size letter (folded, not mailed in 'flat' form) that sends by a common forever stamp, can be simply dropped off at a UPS drop box. This has been offered as a service by UPS to customers at no cost.
To ship a letter or an envelope by ground, which UPS claims in many cases to guarantee to get there by (1) day within the same state, can cost in the vicinity of $12.40 in round numbers which is to send roughly up to one pound on to a residence and just over $2.00 less to deliver to a business address. Noting this is a fee that will vary state by state, envelope dimension and by zip code.
One factor with UPS is that Saturday delivery is ordered by request. This service is available along with next day air and second day air only and the fee is $16 which applies to packages and envelopes. Where the orange Saturday Delivery sticker should also accompany. A way to avoid this added fee is to ship by ground to save on the leap in fee. Although this service is cost prohibitive for many senders, based on the importance and urgency of the particular mailing, it can short-cut some deliveries which might otherwise not arrive until Monday. So planning a day or so ahead can potentially save in the whereabouts of maybe up to thirty dollars or so based on the type of delivery.
Some restrictions, however, are that UPS does observe holidays such as; Christmas, New Years Day and Eve, Thanksgiving, Memorial Day and Independence and Labor Day. There are a host of other holidays that UPS does not recognize and they deliver nonetheless, including on Easter and Columbus Day among others.