Related zu Maaser Sheni 5:17

Second tithe: one may not sell it, use it as a pledge, exchange it, or use it as a weight. One may not say to his friend [even] in Jerusalem: “Here is [second tithe] wine, give me [in exchange] oil, and the same with all other produce. But people may give it to one another as a free gift.

Rabbi Yosei says, Rabbi Meir would say that Kohanim bring but do not recite because they were not given a portion of the land, but I say, just as the Levites were given [their own cities], so too the Kohanim were given [priestly gifts] which obtain both with much and with little (see Sifrei Devarim 165:8, Silverstein).

One may not take terumah from one type on behalf of a different type, but they said (Ter. 2:4), all types of wheat are one, [and] all types of beans, and nuts, and almonds, and pomegranates are one, [and] we [may] take terumah and tithes from one on behalf of the other. [If] someone had black figs and white [figs] inside his house, and similarly, two types of wheat, we [may] take terumah and tithes from one on behalf of the other. Rabbi Yitzchak says in the name of Rabbi Eliezer, Beit Shammai say, we do not take terumah [in such cases], and Beit Hillel say, we [are permitted to] take terumah.

There is a greater stringency with regards to consecrated food [of sacrifices] and Terumah than with regards to the [waters of] purification [containing the ashes of the red heifer], since everyone is believed regarding [the purity status of the waters of] purification, but not everyone is believed as to [the purity status of] consecrated foods or Terumah. There is greater stringency with regards to the [waters of] purification, which is that one who is pure [with respect to the waters of purification] is impure with respect to consecrated food and Terumah, and there is no than with the purity of consecrated food and Terumah. There is a "counting" with respect to consecrated food and Terumah (i.e., 3rd- and 4th- level impurity, see Minchat Yitzchak), but there is no "counting" as to the [waters of] purification. A mourner is forbidden [to partake] in tithes but permitted [to partake] in Terumah and in [the purification rite involving] the red heifer. A tevul yom (i.e., one who has immersed but remains impure until sunset) is forbidden in Terumah but permitted in tithes and in the red heifer. One who lacks atonement (i.e., who has not yet brought a sacrifice) is forbidden in the red heifer but permitted in tithes and in Terumah.

They [may bring their grain to be] milled and stored (מפקידין not מרקידין, see Git. 61b.1) at the place of those that eat seventh-year produce, and at the place of those who eat their own produce in a state of impurity (ibid.), but they may not mill [produce] for those who eat seventh-year produce or those who eat their own produce in a state of impurity.